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Helpful Tips for the 1st Generation Z (1970-1978) Owner

Compiled and Written By Greg McCann

The following is a collection of articles that should be very helpful to the first time owner of a first generation Datsun Z car. The 1st Gen Z’s were the cars manufactured from 1969 until 1978 and was the introduction of these economical yet sporty offerings  from Datsun.  The 240 was manufactured from 1969 until 1973, the 260 was produced for 1974 and the 280 finished out  the first generation models from 1975 – 1978.

 

   Tech Tips  thanks for your help Steve

 

R12 To R134a Retrofit Guide

Note: These retrofits procedures are a combination of OEM and aftermarket recommendations obtained from several sources.

Preliminary System Inspection

If the system to be retrofitted is working, a performance test is necessary. If the system is not operational, then determine what repairs are needed to bring the system to back to operational specifications. Inspect the AC system. Look at the front of the compressor. Is there any oily residue around there? If so, this is an indication the compressor shaft seal is bad. Replacing shaft seals is not difficult, but only if you have the proper tools. If the compressor is over 5 years old, you may as well get a new or a re-built one. R-134a operates at higher pressures than R-12. Older compressors have a tendency to fail when subjected to this increased pressure. Look for oily residue around where the hose connects to the metal lines. This is another sign of leaking. Replace or repair if needed.

R12 Removal and Recovery

Remove any R12 refrigerant in the system using approved recovery equipment. When complete, the system must hold a vacuum for 5 minutes. If the system shows a positive pressure after 5 minutes, then repeat the recovery process.

Oils Used in AC Systems

Mineral oil is used in all R12 systems. It has worked well for years and is still the recommended lubricant for all R12 applications. R12 has a high affinity for mineral oil, meaning it takes the mineral oil with it as it travels through the system. Mineral oil does not mix with R134a and therefore is not usable. Instead, PAG oil (polyalkylene glycol) is used by OEM (Original Equipment Manufacturers) in their R134a systems.
However, polyol ester oil (ester for short) or "retrofit oil" as its sometimes called is the preferred oil to use when you are performing a retrofit. Why? Ester oil mixes with and is compatible with mineral oil and ester oil can be used with both R12 and R134a refrigerants. Ester oil is recommended by most aftermarket manufactures and compressor re-builders. However, it does not provide as good of lubrication as mineral oil when used with R12.

R12 Mineral Oil Removal & Flushing 
Everyone agrees that too much oil will decrease AC performance. So, the more mineral oil that is removed the better. Systems that have signs of debris and contaminants from compressor failure or desiccant
breakdown should be throughly flushed. 

You should remove and flush the condenser, evaporator and the hoses/lines where practical. You should never flush the receiver-drier/accumulator, expansion valve, orifice tube, orifice tube line (or any other refrigerant control valve), mufflers or filters. These are items that need to be replaced. Replace the receiver-
drier/accumulator with one that is designed for R134a systems (contains XH-7 or XH-9 type desiccant).

Likewise, do not flush the compressor. If you are re-using your compressor, then remove it and drain by turning it over and rotating the compressor shaft. Add about a few ounces of ester oil to the suction inlet and rotate by hand to flush out the mineral oil out the discharge outlet of the compressor.

Flush the system with either an AC flushing agent or products such as mineral sprits or paint thinner. Use of mineral spirits or similar solvents is not approved or recommended by OEM or aftermarket manufacturers.
Using mineral spirits may even void the component warranty. Mineral spirits are flammable and are slow to evaporate so some may be left in the system. Because of this, most all OEM's do not recommend that you
flush at all!

However, many AC shop have used mineral spirits to flush AC systems for over 20 years with no problems or come backs. It is a relatively safe product and a good cleaner. It can be purchased from any paint
supplier and at a reasonable price. Mineral spirits are from the same base as mineral oil so small trace of mineral sprits left will do no more harm than R12 mineral oil left in the system after retrofit.

HFCF-141b (Dura 141) is now recommended by most aftermarket AC part suppliers to flush the system, but it is expensive ($70/gal).

Flushing Procedure

* Use a plastic bottle to squirt he solvent into the component.
* Flush in a reverse direction to refrigerant flow first to dislodge any material caught inside. 
* Using shop air at about 60 psi, blow the solvent through the component and catch it in a shop rag. 
* Hold the blow gun tight at one end of the component. 
* Hold our finger over the other end until it builds up pressure. 
* Release your finger letting it blow off (or "pop") pressure. 
* Repeat until there is no sign of solvent coming out. 
* If available, purge the component with nitrogen gas to remove any moisture left behind by the shop air.

Note: Some condensers are very difficult to flush and may need to be replaced. It is cheaper to replace them than to have debris left in the system and damage new components.

System Reassembly

When retrofitting, it is important to remember that most compressors have a pop off or dump valve. This valve will release refrigerant if system pressure becomes excessive. To comply with EPA regulations, a
high-pressure switch must be installed in place of the dump valve to prevent venting the system charge to the atmosphere. In the event pressure gets too high this switch will instead shutdown the compressor.  However, lots of parts stores still don't stock them (and some parts stores still don't know what they are).  You may have to try more than one parts store. If your system has no pressure relief or dump off, no switch is required. However, it is good safety measure to install one, just in case.

When you do have to change the compressor make sure you know what type oil the new or re-
manufactured one contains. Most re-builders use ester oil but some now sell compressors with no oil in them. So, always check. If the compressor is replaced, installation of an in-line filter on accumulator type systems may be required to validate the compressor warranty.

Installation of R134a only service port fittings is required by law. These fittings are included in a "retrofit kit" available from most automotive parts stores. Any leftover R12 service ports not in use should have block-off caps put on them. These caps should have a thread lock on them to prevent removal. The 90 degree service ports must have the valve core removed. 

Make any other necessary system repairs. Check the condition of expansion valve, orifice tube and pressure switches. Any o-rings and gaskets should be replaced with R134a type (included in the retrofit
kit). Coat all o-rings, seals and fittings with system oil or Nylog lube. The aftermarket and the OEM manufactures recommend that you don't need to change the hoses unless they show signs of leaks. If you
replace the hoses, it should be with "barrier" style hose and "beadlock" fittings.

Note: Keep the new accumulator/dryer closed up until the last possible minute.

System Oil Fill

Pour 4 oz's of oil down the compressor suction port. Put 1 oz in condenser, 2 oz's in evaporator, and the accumulator/receiver-dryer gets 2 or 3 oz's. Total system oil charges vary. If you need info, check your service manual or find a source on the internet. 

Reassemble the system and pull a vacuum. Once you have a good vacuum, turn the compressor over by hand a full 12 to 14 revolutions. This will clear any oil on top of the compressor pistons. Continue pulling down a vacuum for about 40 to 60 minutes. Turn the vacuum pump off and watch the gauges. The system should hold vacuum. If it doesn't, check your gauge connections and then all the system fittings. 


Charging with R134a

Connect your AC gauges and add the R134a refrigerant. R134a is very unforgiving, so start low. Find the label on your vehicle that shows the R-12 charge. Convert to ounces. Take 70% of this number for the
initial charge amount. Example: R-12 charge = 2.5 lbs. Take 2.5 lbs. x 16 oz's = 40 oz's. 70% of 40 oz's = 28 oz's. You may have to add just a little later on. However, I have discovered that 70% plus 1 or 2 oz's
seems to work out very well.

Start the car and turn AC control lever to maximum. Turn the fan speed down to low. Stick a thermometer in the cold air outlet vent. Set engine rpm at 1500 to 2000. Add additional R134a 1 ounce at a time until you reach maximum cooling. When the air outlet temperature starts to go up, remove what you just added. 

Watch your gauges. Wait for compressor to cycle. Fan speed set on "low" should let it. When it does cycle, make note of the low side pressure. Compressor should cycle out around say 22 psi. If it cycles at
25 psi, look at the vent temp. Is it close to 40 degrees F? If not, remove plug on low-pressure switch, located on accumulator, or low-pressure line. Using a small flat blade screwdriver, turn the screw inside the pressure switch 1/8 to 1/4 turn, counter clockwise. Usually 22 psi low side pressure is plenty good. Don't get carried away. Try not to go below 18 psi. If you set the pressure too low, the system will freeze up. I've seen 40 degree air at 25 psi. Plug the connector back in. If the vent temperature is around 40 or a little more, you're good to go. Some vehicles have non-adjustable pressure switches.

You will see bubbles in your receiver/drier sight glass even with a full charge of R134a. This is normal. 


R134a Cooling Problems

One of the major problems with retrofits to R134a is high head pressure caused by poor heat exchange at the condenser. Any heat exchange and air flow improvement you can make will only help the operation of the AC system. Make sure the condenser has clean fins and good air flow. Add seals around the condenser to improve the air flow through it. Increase the air flow by adding a engine fan shroud, changing the engine fan clutch to a heavy duty type or adding an auxiliary electric cooling fan in front of your condenser. Wire it so it turns on with the compressor clutch. In addition make sure that any air dams, belly pans, etc. are not missing. 

You should know that an air conditioning system converted to R134a will never cool as good as it did with
R12. At it's optimum a 134a retrofit should get you to within 3-5 degrees Fahrenheit (cold air outlet temperature) of the R12 system. R134a refrigerant is about 10% less efficient in removing heat than R12.
This refers to BTU's (heat) moved per pound of refrigerant moved. The general practice of charging the system with 15% less refrigerant adds to the thermal deficiency of R134a

There are also rumors that R134a is more likely to leak through hoses due to its different molecular composition. But the hoses are so thick that, while technically correct, it's not a practical issue. Even if it
does leak, it's a slow leak, you can replace a lot of R134a for the price of new hoses. 


Improved Condensers

The need to change the condenser to a better type will be done on a vehicle by vehicle bases. The need will depend on the climate, conditions of use, the size of the vehicle, and the other components such as the evaporator. If it is necessary to replace the condenser, try to use a newer improved version (multi-flow model). The head pressure of the air conditioning system will tell you if the old condenser is sufficient. Any head pressure over 250 PSI will hamper cooling and any head pressure over 325 PSI should be considered
overheating. Air conditioning manufacturers have made significant design changes to condensers for use with R134a. The design changes provide more heat exchange by being larger and having more vaporous flow capacity. Many companies that make add on air conditioning systems found they could not use conventional serpentine R12 condensers with R134a.  Serpentine condensers have very small continuous passages that zig zag through it like a snake. New
serpentine condensers are available and are advertised as being ideal for a R134a retrofit. They are advertised as having a six channel serpentine tube that provides more primary heat exchange surface than the typical four channel tube. 

You may notice that R134a condensers have more flow capacity for the vaporous part of the refrigerant.  "Multi-flow" condensers as they are called, have a header that is connected to at least four passes at the top of the condenser. This is reduced gradually until there is only one pass at the bottom of the condenser.  By the time the refrigerant reaches the bottom of the condenser it should be liquid and should not need as much room. Parallel flow condensers are condensers are a cross flow design, with the header on the end connected to all passes. The are made out of aluminum and are very efficient.

Four Seasons, Modine, Rahn Industries and Superior Manufacturing Corporation all make OEM R13a and retro-fit condensers.


Closing Remarks 

Install the special "System Contains R134a" service labels (that meet SAE requirements) in a visible location in the engine compartment. These are required by law. Lastly, leak test the system using
equipment that will detect R134a refrigerant.


Replacing Your Original Z Seats with 240SX Seats

Things you will need: at least 12 ft of 1/4" x 1" aluminum molding,
hack saw, drill (or drill press if available), tap and die set,
lots of patience, cold beer.

Step 1. Find a good set of 240SX seats in a junk yard. I paid $100
for an immaculate pair. The 240SX seats have "Zip-on, Zip-off"
upholstery that can probably be ordered for replacement if
necessary.

Step 2. Remove the original glide hardware from the 240SX seats. It
will not even begin to fit in your Z. Be careful and replace all of
the bolts you remove to take off the glides. They hold the seat
together You will have to add one more bolt on the "inside" side of
each seat. When you remove the glide, you remove part of the hinge
that holds the top part of the seat to the bottom. The extra bolt
will keep the hinge from shifting (you will see what I'm talking
about if you do it!).

Step 3. Take your original Z seats out of your Z. Take the glides
off the bottom. You will have to retro-fit these glides to the
240SX seat. This can be particularly frustrating since the glides
are held on by very tight phillips head screws. I had to take a
pair of vise-grips and a large screwdriver to break them free.

Step 4. Get at least 12' of aluminum molding 1/4" x 1". You can
pick this stuff up at any Home Depot or Lowe's Home Center. I chose
aluminum because it is much easier to work with. You could use
steel if you had access to the right tools. Measure the width of
the 240SX seats. You want to cut 8 identical pieces of aluminum the
width of the 240SX seat.

Step 5. These next steps will be up to you. I kind of fit
everything as I went along. I measured the distance between the
mount holes on the original Z seats. I drilled holes in the
aluminum that were that distance apart and equal distance from the
ends. This will allow you to bolt the glides to the mounts. For
ease, I tapped these holes so I would not need a nut to hold the
bolt in place.

Step 6. Now that you have the holes drilled in the aluminum slats.
Bolt them to the glides and line them up on the bottom of the 240SX
seat. Square up the glides and mark where holes can be drilled into
metal on the bottom of the seat. Drill the holes through the
doubled aluminum. Then mark where the seats should be drilled and
drill them.

Step 7. Take the glides off of the aluminum slats. Bolt the
aluminum slats to the seats. Be advised, getting the nuts between
the seat metal and the seat foam is hard on the hands. If you
tapped the holes for the seat glides you can now bolt the glides to
the aluminum slats on the seat. It is useful to put a 1/4" spacer
between the slats and the glide for ease of movement.

Step 8. Hopefully, if you were careful to note the alignment of the
glides throughout the process you will be ready to install the new
seats. Place them on the original beams in the passenger
compartment. They should bolt right up. Note, the fit is a little
tight on the door side of the seats. You can do some handy Xacto
knife work on the 240SX plastic seat facing to cover it up.

Step 9. Try seats out. Get comfortable. Drive around. You will
instantly feel better, and your life will immediately improve. Go
home, get the beer out of the fridge and enjoy several cold ones
for a job well done.

Fog Lights For Your 240Z

I have a question concerning my '70 240. Located right above the
hazard light switch on the dash is a "depression "for which I have
no clue of its purpose. I have seen this depression on a '71 240Z
as well.

This "depression" is for a driving lights or fog lights switch that
was available on European and Japanese models.

The US models have the male/female plugs for the driving lights,
wrapped up in electrical tape already in the wiring harness. If you
feel the harness, right along the lower valance pan under the front
bumper (right by the horns) you will feel a "lump" in the harness.
Unwrap the blue tape there, and you will find the "plugs" for the
driving lights.

The switch connectors under the dash. They are wrapped in blue
tape just like the connectors for the fog lights, and are located
in the wiring harness right behind the oil pressure/water temp
gauge. I recently installed some driving lights in my Z. I bought
an automotive toggle switch at Radio Shack, and installed it in the
"depression" hole in the dash. The switch connectors on the factory
harness fit perfectly on the terminals of the Radio Shack
switch.

Then I wired up the lights using the factory connectors and the
original holes under the bumper. Works great, and looks like a
factory installation! Plus, the lights turn off with the parking
lights, so you can't accidentally leave them on all the time.

Tech Tip
Retractable Seat Belts for your 240Z

I would like to put the retracting shoulder/lap seat belts on my
240Z. Can this be done? I assume the later Z's had this feature?

First, some background: The 1970 and '71 240Z's had non-retractable
belts for both lap belt and shoulder belt. The shoulder belt could
be separated from the lap belt and the lap belt could then be used
by itself.

Starting with the '72 240Z's that had a production date of 1/72,
Nissan added a retractable lap belt mechanism. The '73 240Z's also
had the retractable lap belt but the shoulder harness belt remained
NON-retractable, until the 1974 260Z's. However, once you're
buckled in, you generally want the lap belt to stay tight, but when
backing up in reverse, or reaching for the radio, one needs to lean
forward a bit. So, Nissan did it backwards with their first seat
belt retractors in the Z cars!

For the '74 260Z and later Z's Nissan also installed a retractor
for the shoulder strap, along with the lap belt retractor. Unlike
the earlier cars, the lap belt and shoulder belt ends are riveted
together at the buckle. On the '74 and '75 cars the new shoulder
retractor mechanism bolts up right where the original shoulder belt
was attached. The '76-'78 280Z's moved the shoulder retractor
mechanism to the top of the strut tower.

When the lap belts went retractable, a sheet metal "pocket" was
added in the floor pan just in back of the outboard edge of the
each seat to house the belt mechanism. It is interesting to note
that an empty "pocket" was first added to cars with a production
date of 9/71, but the retraction mechanism was not added until
1/72! So, any 240Z produced prior to 9/71 would not have the
pockets for the lap seat retractors. The 1974 260Z's and '75 280Z's
lap belt retractor mechanism is larger, so the pocket in the
floorboard is larger than the '72 and '73 cars.

So, if your 240Z was built between 9/71 and 1/72, you can easily
add the lap seat retraction mechanism from a later '72 or a '73
car. This won't work for the earlier cars as they don't have the
pockets in the floor pan. Although one could cut a couple holes,
and cut the pockets out of a later car, and weld them into the
earlier car, there is an easier solution: Get the seat belts from
a junk '74-'78 2+2 Z car and separate the lap belt from the
shoulder belt by drilling out the large rivet that connects them.
The 2+2's did not have the pockets because if they had them, they
would have interfered with the feet of the rear passengers. Their
mechanism bolts to the bottom side of the rocker sills.

The 2+2 retraction mechanism then bolts to where the '70 and '71
lap belt bolted to. If you also want the retractable shoulder belt,
then get the shoulder belt mechanism from a '74 or '75 2-seater.
Again you must drill out the large rivet at the buckle and then you
can re-join the lap belt to the shoulder belt with a nut and bolt.

Now, if you want to add the retractable shoulder belt to the '72
and '73 cars, again use one from a '74 or '75 2-seater and follow
the same above procedure.

5 speed transmission installation tip:

I just put a 5 speed transmission from a 280Z into my 240Z
without switching the clutches and it now appears that the clutch
is not fully engaging! What's wrong?

The "installed height" of the clutch disc and pressure plate
combination is different between the 240Z and the 280Z. To make
up the difference, Nissan changed the length of the throwout
bearing collar, the piece that the throwout bearing is pressed
into.

Whenever you swap transmissions on a Z car, the safest course of
action is to use the clutch/pressure plate with the throwout
bearing collar that it was originally installed with. In other
words, treat the clutch/pressure plate with the throwout bearing
collar as a "joint" unit. Then you will have no problems. It
sounds likes you did not do this!

I'm afraid that I have no "quick fix" for you. You will have to
drop the tranny (again!) and either use a 280Z throwout bearing
collar or replace your clutch/pressure plate with a 280Z type.

 

Flywheel

I was wanting a lighter flywheel for my Z, but I was surprised at
the very high cost ($350+) for the Centerforce 13 lb one. Is there
a flywheel weight in between the stock 24 lb and this 13 lb one
that I can use?

Yes there is! The flywheel from the 7/78 to 6/84 production date
Datsun 810's and Maxima's had a lighter 17.6 lb flywheel, part
number 12310-Y7000. So, these are the one's to locate if you're in
search of the lighter flywheel. The 810/Maxima flywheel can be
identified by the "Y70" cast into the backside of the flywheel.

Most junkyards remove the flywheel from engines and will sell them
separately. Just make sure the clutch disc surface is not worn
excessively. Small groves can be machined out. Check for wear on
the starter gear ring. The ring gear can be replaced, but since
this will cost much more than a good used flywheel, avoid getting
a flywheel that needs the ring gear replaced.

The Maxima/810 flywheel takes the 225mm clutch which was the same
size as the 2-seater Z car clutch.

Servicing your AC

It's hot, so hot your Z's dash shimmers. You carefully get into the
car so as not to raise blisters by touching the steering wheel and
you start the engine. You turn the AC on but nothing happens!!
Great, you think, at least in the "old days" ordinary folks could
purchase R-12 refrigerant to re-charge their system, but not
anymore.

Fortunately, it's still possible for the average backyard mechanic
to repair or diagnose most of what ails his Z car's air
conditioning system. Start by acquiring the Nissan factory service
manual for your particular Z and read up on the AC section. It's an
excellent write up. You'll also need a good volt-ohmmeter and a set
of AC gauges. A thermometer is also handy.

No Cooling at All

If the engine driven compressor doesn't engage, there will be zero
cooling. An electromagnetic clutch on the front of the compressor
should lock the drive plate on the compressor with the belt driven
pulley to spin the compressor shaft.

To check the operation of the clutch observe if the compressor
drive plate is rotating when the AC is turned on. The clutch
usually makes an audible "clunk" just as it is engaged. If the
clutch is not engaging, then check the AC fuse to see if it is
blown. If the fuse is blown then replace it and if it blows again
you may have a defective clutch. Measure the resistance of the
clutch coil winding and compare it to the value listed in the
service manual. If your clutch coil measures much below (or much
higher) than what is listed in the manual, then it is probably
defective. It takes special tools to remove a clutch and it's coil
winding. Unless you can rent them or borrow them, leave this job to
a pro.

Connect a test lead from the 12V terminal at the battery to the
blue wire that goes into the compressor. If the clutch does not
engage, then the clutch coil winding is open. Confirm this with a
resistance measurement. If the clutch then engages, you have an
electrical problem.

The electrical circuit consists of a AC compressor relay located in
the engine compartment that is first energized to complete the
circuit to the clutch coil. There is a fuse in this circuit. In the
AC relay circuit there is a micro switch activated by the AC
control lever, a "low pressure" cut out switch, and a thermostat
switch that cycles the compressor to regulate the temperature. In
addition, the interior blower fan must be turned on in order for
the circuit to work. So, there are a lot of possibilities for an
electrical problem which you can troubleshoot yourself with a volt-
ohmmeter.

However, the refrigeration system may also be involved. The low
pressure switch located in the receiver/dryer unit is designed to
keep the compressor from engaging when the freon pressure is low.
Unplug the wiring connector from this switch and use the volt-
ohmmeter to see if it is closed.

If the switch checks open, then connect the AC gauges to the
Schrader valves to measure the freon pressures in the system.
Remember, the "high" side (or "discharge" side) of the compressor
connects to the red gauge, and the "low" side (or the "suction"
side) of the compressor connects to the blue gauge. After the
system has been off for a few minutes, the high and low side
pressures equalize and the system pressure is a function of the
ambient temperature. If the pressure is less than 35psi, then the
system is low on freon and needs a re-charge. Proceed to the re-
charging section. However, the reason the system is low on charge
is probably due to a leak.

Now the best way to find a leak is to pressurize the system with
freon and use a leak detector. However, sometimes a leak can be
spotted visually. There is oil mixed in with the freon to lubricate
the components in the system, and when you have a leak this oil can
be seen. Usually the oil attracts a coating of dirt so look for a
"dirty oil-soaked" stain. Some areas for leaks include the
condenser (damage from road debris), loose hose fittings and a
leaky front compressor seal. Incidentally, if the Schrader valve
caps are missing, they could be the cause of your freon loss, as
they provide the real seal, and not the valve itself.

Poor Cooling

If there is some cooling, but clearly not a normal amount, then
there are a few initial checks you can make. Is the condenser free
of bugs, leaves or road dirt? If it isn't, then airflow is
restricted. Clean the condenser with a soft brush and a detergent
and water solution.

The engine radiator fan and or an electric supplemental radiator
fan may be defective, reducing the air flow across the condenser
coils, although this usually results in engine overheating as well.

It is possible that the heater core is circulating hot water
because of a leaky or stuck open watercock valve. Use a pair of
vice-grips to squeeze off the heater core supply hoses in the
engine compartment to check for this.

However, the majority of the time a case of poor cooling is a
result of a low level of freon in the system. The receiver/dryer
unit has a "sight glass" on it's top to allow a look inside the
system. With the AC turned on, check the sight glass for bubbles.
A continuous flow of bubbles means the system probably is low on
charge. No bubbles can either mean no charge or too much charge.
You have to put the AC gauges on to correctly verify the state of
the charge.

Because of the nature of AC systems, the readings on the gauges for
a fully charged system are a strong function of the outside ambient
air temperature and the relative humidity. There is a chart in the
service manual to assist you. For example, a 1974 260Z at a
relative humidity level of 70% has the following measurements:

Outside Air Discharge Air High Side Low Side
Temperature Temperature Pressure Pressure
(degs F) (degs F) (psi) (psi)

70 49 to 55 154 to 182 24 to 33
80 57 to 64 168 to 202 28 to 37
90 63 to 71 192 to 228 34 to 43
100 70 to 78 219 to 255 43 to 51

The discharge air temperature is measured by inserting a
thermometer into one of the ducts. Make your measurements at the
maximum cold setting and at the highest interior fan speed. The
engine should be at a fast idle, 1,500 rpm or so.

If the high side pressure is lower than what the chart says, then
there is an insufficient amount of freon in the system. If you were
lucky enough to have obtained so cans of R-12 freon before it
became illegal to buy without a license, you can add some to your
system. With the gauges connected to the appropriate Schrader
valves, attach the center hose to the can of R-12 using the adaptor
that pierces the top seal on the can. A tip to speed up the
recharging process is to immerse the can of R-12 into a pan of warm
water.

With the engine running and the AC on, open the low side valve to
allow the freon to flow from the can into the system. Keep a eye on
the sight glass and when the bubbles cease to be visible, stop the
recharging. Do not over fill, as this will reduce the cooling
capability of the AC system. If one can of freon is not enough,
then another can be started. When completely empty, the system will
hold two of the one-pound cans of freon.

Other Problems
Poor AC cooling can be caused by the cooled air not flowing out the
correct duct in the passenger compartment. It's much more effective
to have the cold air blowing in your face, and not at your feet or
going through the defroster ducts.

Z cars use a vacuum system to operate the various air control vent
doors. The vacuum is generated by the engine and a one way check
valve and stored in a plastic bottle in the engine compartment. An
electrical solenoid directs the vacuum flow. Early Z cars are
notorious for engine compartment vacuum hoses that crack due to age
and heat. A bad check valve can allow the system to work at idle
speeds, when you have a large vacuum in the intake manifold, but as
the throttle is depressed, the intake vacuum goes away and the
vents stop working.

The interior blower fan speed may not be high enough. Leaves and
other debris (I once found a mouse's nest in there!) can enter the
blower intake and reduce the air flow. Resistance at the fan motor
electrical contacts can reduce the voltage across the blower motor.
Check all the electrical connections between the battery and the
fan for any excessive voltage drops, including the fuse and fusible
link.

Check the condition of the ductwork seal between the output of the
blower housing and where it joins the diffuser section behind the
evaporator. This seal tends to dry out over the years.

The AC compressor belt adjustment pulley has a bearing that can
seize and not allow the compressor to rotate. This is a common
problem on high mileage Z cars. Keep on eye on this adjustment
pulley and replace it if it starts to become noisy.

A Final Word

Don't expect the '70-'78 Z car AC systems (factory or dealer
installed) to perform miracles. The later 280ZX and 300ZX systems
are much better performers. If your AC system is working overtime,
and you're still sweating it out, consider window tinting, it
really helps. Also, increases the thickness of the floor and
transmission tunnel carpeting (or even adding some there) helps to
keep unwanted heat from entering the passenger compartment.

 

What to look for when buying a battery.

Cold Cranking Amps

The most important consideration is the battery's Cold Cranking
Amps or COCA rating. CCA's are the discharge load measured in amps
that a fully charged battery at 0 degrees F can deliver for 30
seconds and while maintaining the voltage above 7.2 volts.
Batteries are sometimes advertised by their Cranking Amps (CA)
measured at 32 degrees or Hot Cranking Amps (HCA) measured at 80
degrees, which are not the same as CCA. Do not be mislead by CA's
or HCA's. To convert CA's to CCA's, multiply the CA's by .8. To
convert HCA's to CCA's, multiply HCA's by .69. In hot climates,
buying batteries with double or triple the CCA ratings that exceed
the OEM (original equipment manufacturer) requirement is a WASTE of
money. However, in colder climates the higher CCA rating the
better, due to increased power required to crank a sluggish engine
and the inefficiency of the cold battery.

Reserve Capacity

The next most important consideration in buying a battery is the
Reserve Capacity (RC) rating because of the effects of an increased
parasitic or "key off" load produced by electrical devices, e.g.,
fans, clocks, computers, etc., that operate after the engine is
stopped. RC is the number of minutes a fully charged battery at 80
degrees F can be discharged at 25 amps until the voltage falls
below 10.5 volts. More RC is better in every case. For example, if
your car has a 360 OEM cranking amp requirement, then a 450 to 500
CCA rated battery with 120 minute RC would be more desirable in a
warm climate than one with 700 to 800 CCA with 90 minutes of RC.

Type

A sealed or "maintenance free" battery will NOT allow you to test
the specific gravity with a hydrometer or add DISTILLED water when
required. Sealed batteries are more prone to deep discharge
failures, but require less preventative maintenance. Car batteries
are specially designed for high initial cranking amps (usually for
five seconds) to start a car; whereas, deep cycle or "marine"
batteries are designed for prolonged discharges at lower amperage.
A "dual marine" battery is a compromise between a car and deep
cycle battery. However, a car battery will give you the best
performance in a car. Some manufactures have introduced a "dual"
battery that combines a standard battery with emergency backup
cells.

Physical Size

Manufacturers build their batteries to an internationally adopted
BCI group number (24F, 35, etc.) specification, which is based on
the physical case size, terminal placement and terminal polarity.
The OEM battery group number is a good starting place to determine
the replacement group. Within a group, the CCA and RC ratings,
warranty and battery type will vary in models of the same brand or
from brand to brand. Batteries are generally sold by model, so the
group numbers will vary for the same price. This means that for the
SAME price you can potentially buy a physically larger battery with
more RC than the battery you are replacing. Be sure that the
replacement battery will fit, the cables will correct to the
correct terminal, and that the terminals will NOT touch the hood
when closed.

The battery manufacturers publish application guides that will
contain the OEM cranking amp and group number replacement
recommendations by make, model and year of car, and battery size,
CCA and RC specifications. Manufacturers might not build or the
store might not carry all the group numbers. To reduce inventory
costs, dual terminal "universal" batteries that will replace
several group sizes are becoming more popular. The four largest
domestic battery manufacturers are Johnson Controls (Interstate,
Motorcraft, Energizer, older Diehards), Delco (Sears, newer
Diehards), GNB (Champion) and Exide (NAPA).

Age

Determining the "freshness" of a battery is sometimes difficult.
NEVER buy a battery that is MORE than SIX months old! The date of
manufacture is stamped on the case or printed on a sticker. It is
usually a combination of alpha and numeric characters with letters
for the months starting with "A" for January (skipping "I") and
digit for the year, e.g., "F5" for June, 1995. Like bread, fresher
is definitely better.

 

Tech Tip

Is it possible to remove the cam towers from the cylinder head and
re-install them without having to worry about alignment? The
service manual says that this is a "no-no".

The locator sleeves between the head and the cam towers do a fine
job of getting the towers lined up again. In fact, if you look at
a head that has been shaved or milled, it should have correction
plates/shims that are inserted under the towers to ensure that the
timing chain "slop" remains within spec. Depending on how much you
mill, it would be difficult to take up all the slack with the chain
tensioner.

The key to installing the towers is to install the cam AND towers
together. Then go through steps in torqing the bolts which secure
the cam towers to the head, so all the towers are torqued evenly.
Starting with a low torque setting, and follow a couple more times,
increasing the torque setting each time, checking for smooth, light
cam rotation. If necessary, tap the bearings with a mallet to
smooth things out, then repeat the procedure until the cam tower
bolts are torqued to spec, and the CAM TURNS FREELY! Install the
cam followers to finish the job.

The How to Modify your Nissan/Datsun book by Frank Honsowitz
recommends the above method.

What are the symptoms of a clogged catalytic converter?

The most noticeable symptom will be a lack of power. You step on
the gas and your Z car doesn't get up and go. A badly plugged
converter may not even let the vehicle go over 30 mph. The
converter will be hotter on it's intake side if it is plugged and
may even glow a dull red if the engine has been running a while.

Here's the simple procedure for testing for a clogged catalytic
converter

1. Connect a vacuum gauge to a vacuum line fitting on the intake
manifold. The easiest access points are either the off the vacuum
fitting going to the brake booster check valve or the vacuum hose
fitting for the charcoal canister purge valve.

2). Record vacuum at idle (usually over 17 inches of Hg).

3). Record vacuum at 3000 rpm with engine at no load.

4). The vacuum reading taken in step 3 should be at least as great
as that taken in step 2. If the vacuum reading in step 3 starts
dropping (even going positive) from its original reading, then you
could have a clogged converter.

This is an indirect test -- a better one is to use a backpressure
tester. This is a vacuum/pressure gauge with an adaptor which
allows the tester to be screwed into the oxygen sensor's socket.
At 3000 rpm, the backpressure should be below 3 psi. You can buy
these at your local automotive parts place for $25-30.

Tech Tip
Finding Coolant Leaks

When it comes to coolant leaks, do the common sense stuff first.
For example, monitor the level and activity of the coolant
reservoir. When the engine cools down, the low pressure in a tight
cooling system should draw coolant in from the reservoir. What's
more, the reservoir coolant level on a hot engine should be
consistent if the cooling system is leak free.

Locating a small leak can be difficult because the coolant often
evaporates as soon as it leaks out. Pressurize the system with a
hand operated pressure checker and give it a thorough visual
inspection. It could take a while for a pinhole to create the
telltale stains you search for during diagnosis.

Hunting for leaks with a hand operated pressure checker can be time
consuming because you have to keep pumping the thing up to maintain
pressure on the system. Pressure testers that rely on shop air
eliminate manual pumping, allowing you to keep your eyes focused on
suspected leak points. Wear protective goggles when hunting for
coolant leaks.

Remember that checking the system cold may reveal a leak you can't
find when the system is hot. It's well known that problems such as
leaking water pump seals are more likely to occur when the engine
is cold.

Adding a fluorescent leak-detection dye to the coolant is the most
accurate way to locate elusive external coolant leaks, including a
seeping water pump concealed by other engine components. Leak
tracing dye also is a great quality control tool because a dye
check after a repair is completed shows you that the troublesome
leak is finally fixed.

Note three details about the dye method: First, you must clean up
existing dye stains before retesting. If you don't, you won't know
if you're looking at a recurring leak or dye lingering from the
previous leak. Some techs just use solvent for this task. As of
this writing, one manufacturer (Tracer Products) offers a water
based, nontoxic spray cleaner for removing fluorescent dye.

Second, you need a UV (ultraviolet or "black light") lamp to spot
fluorescent dye. The more powerful the black light, the easier it
is to see dye traces on a dirty engine inside a dark engine bay.

Third, UV lamps are fairly large and tough to maneuver inside a
crowded engine compartment. Today, at least one compact, flashlight
size UV light (Tracer Products again!) is available for automotive
leak detection.

The ease of pinpointing a coolant/combustion leak depends on the
severity and location of the leak. Begin by checking for pressure
buildup inside the coolant reservoir and/or a persistent sweet odor
of antifreeze in the exhaust.

Comparing spark plugs can help flag an internal coolant leak. Look
for a plug that's noticeably cleaner than the others with no carbon
deposits on it, with the porcelain around the center electrode
looking almost spotless. Inspect the combustion chamber that spark
plug came from with a small dental mirror and a shop light. You'll
find the chamber also looking unusually clean due to the steam
cleaning action of the coolant leak.

Antifreeze in the exhaust taints the oxygen sensor, turning the tip
of the sensor green or a grainy, brownish white color. Eventually,
leaking coolant also can contaminate and clog a catalytic
converter.

Looking for combustion gas bubbles inside the radiator can be
misleading. It's easy to mistake air venting or even a sticking
thermostat for combustion bubbles.

Connecting a coolant pressure gauge to the radiator neck can
confirm a coolant/combustion leak. Cooling system pressure should
remain fairly stable as you rev the engine. Pressure readings that
either climb or drop into a vacuum when you snap open the throttle
suggest cracks in the valve seat area.

Finally, you can pressurize each cylinder with compressed air and
see if bubbles appear in the radiator. If you use this air check,
remember that some leaks are more noticeable when the engine is
cold.

Tech Tip

Why does the interior of my early Z car smell like exhaust fumes? It's
especially bad with the windows open?

As a car is moving down the road with the windows up but with the vents open,
the air pressure in the passenger compartment tends to increase. This is because the vents are in front of the radiator, which is a high pressure area.  If the windows are rolled down this pressure is reduced and may even be slightly negative. This lack of pressure "allows" the exhaust gases to enter the passenger compartment by any opening they might find.

The usually place of entry is the rubber rear hatch seal. These tend to lose their seal over the years. The solution here is to buy a new one.
Unfortunately, the rear hatch seal is very expensive, so you may be able to adapt a similar sized generic weatherstrip.

Don't overlook other possible leaks: The openings where the fuel tank vent lines go through the body of the car. Silicone these if they look suspect.  Also, the gaskets on the rear taillights can leak, allowing fumes to enter.  Replace them or use silicone if your a cheapskate.

Another possible leak is the gear shifter boot. Pull the console out to check this. Also, you can seal up the rear hatch latch mechanism from the passenger compartment. Make a gasket from some flexible plastic material and silicone it around the latch.

If all these suggestions fail, then you can try extending the exhaust tailpipe by some six to ten inches past the bumper. You can even angle the exhaust tailpipe to the left, away from the car, as this also seems to help.

 

Tech Tip
Flushing Your Cooling System

You take off the radiator cap and look at the coolant. It's usually
a nice shade of green, but nowadays you can find red and maybe even
orange or bronze tinted fluid. Well, it looks good. So, should you
leave it in? Unless it's colored orange or bronze stuff, the answer
is NO! Especially if it's been two years or more since the last
time you drained it.

Z car engines are loaded with aluminum components: cylinder
head(s), water pumps, front engine covers, manifolds, heater cores
and even some of their radiators. Aluminum needs great corrosion
protection to survive, and the corrosion protection in the green
and red colored antifreeze is used up in about two years. However,
the orange or bronze colored coolant does offer longer life. More
on that, later.

Draining the Coolant

Start by checking your service manual to see how much fluid is in
your system. This is important, because Z cooling system capacities
varied depending on the generation. Also, if you have increased the
size of your stock radiator (e.g., from a three core to a four
core), you will have to account for this.

Be safe and start with a cool engine. Set the interior heater
control lever to the HOT position. This will allow the heater core
to drain. If you have a radiator overflow reservoir, then remove it
and drain it as well. Now remove the radiator pressure cap and open
the radiator drain cock. You can use a pair of pliers to reach a
difficult-to-reach one (like on the 300ZX's) or to free a stuck
one, but be careful. Remember, the Nissan drain cocks are made of
plastic, so they're easy to break!

If the drain cock is really stuck, or broken off flush with the
bottom of the radiator, then you can disconnect the lower radiator
hose from the radiator to drain the coolant.

Let the used coolant drip into a container or pan. If your house
has a city sewer disposal system, then you are allowed to empty
your old anti-freeze into your drain. Don't just pour it on the
ground or into a septic tank system. Better yet is to take it to
one of the hazardous waste disposal facilities in your are, or you
can nicely ask a auto repair shop to dispose of it.

Draining the radiator alone will only remove about half of the
coolant. There is an engine drain plug located on the side of the
block. Removing this will allow the remainder of the coolant to
escape. It's messy, but it's the preferred way.

Refilling

First, tighten the drain cocks and any hoses you may have removed.
Check on the side of the new container of antifreeze for how much
antifreeze you actually need. Now most people just put the
"standard" 50/50 (half water and half antifreeze) ratio back in
their system, but I recommend using only as much antifreeze as
necessary. The reason for this is the fact that water by itself is
a much better conductor of heat than antifreeze!

It is generally recognized that straight water will cool a car more
effectively than any combination of water and antifreeze, despite
antifreezes marginal increase in boiling temps. So, the old adage
of "if some is good, then more is better" does not apply with
respect to antifreeze. There will still be plenty of anti-corrosion
inhibitors and water pump lubricant even with a 20% ratio of
antifreeze.

What about using distilled water with the antifreeze instead of
ordinary tap water? The reasoning here is that normal tap water has
minerals dissolved in it. Through repeated heating in your car's
cooling system, those minerals will eventually precipitate and form
hard deposits in the radiator, especially in small passages.
Distilled water is free of minerals, and therefore will not have
this effect.

However, now the reasoning is to use regular tap water because
water normally likes to have ions floating around. If it doesn't,
then it gets them from wherever it can. Aluminum readily ionizes,
so the distilled water "steals" the ions from the aluminum
components and they corrode. If you use tap water, it is "pre-
ionized", so to speak. The tap water will sacrifice itself, and not
your engine parts, to the chemical reactions created during thermal
cycles of the fluid and metal parts.

The cooling system has nooks and crannies that can trap air. The
filler neck is supposed to be at the high point to let air out, and
there is a small hole in the thermostat to allow trapped air to
escape. Fortunately, Z cars are not known to be hard to refill with
coolant and air pockets generally do not occur.

Slowly pour the antifreeze and water into the radiator until it is
full. Now you probably won't completely fill the system initially.
Start the engine and let it idle until the thermostat begins to
open. The water level in the radiator will invariably go down. Add
some more water or antifreeze until it is full. Remember only add
water to a hot engine while it is running! Better still is to warm
the engine with the radiator cap on, let it cool and then check the
fluid level. Check the fluid level periodically over the next
several days.

Which Antifreeze To Use?

Most antifreeze is made with a colorless base chemical called
ethylene glycol. A green dye is used in most brands, although there
is a Toyota brand which is red. The latest entry into the market
are the "long life" types of antifreeze which are tinted orange or
bronze (e.g., Prestone Long Life 5/100, or 4/60). These are good
for four to five years.

If you are changing from the "green stuff" over to one of the long
life antifreezes, then you must thoroughly flush out your cooling
system first. The corrosion inhibitors in the green and the
orange/bronze antifreezes are not compatible. After you have
removed the green antifreeze put back in only water. Let the water
circulate. Let the engine cool and re-drain the water. Repeat this
twice more.

It's a good idea to make sure that the antifreeze is a "low
phosphate" type. The presence of phosphate in your coolant will
force the concentration of aluminum ions to be extremely low. This
will tend to increase the rate at which aluminum metal components
of the engine will oxidize (corrode) into the coolant.

The aluminum phosphate formed will tend to collect in your cooling
system and will NOT flush out. This could impair the efficiency of
heat transfer and reduce water flow rates through the system.

So to be safe, use a phosphate free coolant. Read the label on the
antifreeze container. If it says "phosphate free", it should be OK.
If it says "safe for aluminum engines", it should also be OK. If it
doesn't make one of these claims, then find another variety.

What about the "pet-friendly" antifreezes? These use a base of
propylene glycol and will do the same job as ethylene glycol. They
cost a little more and require a greater quantity to provide the
same protection and they're really only a bit less hazardous. Their
real claim is that they don't have a "sweat" odor or taste (I
wonder who found this out!) and therefore are less likely to attach
pets or small children.

Tech Tip:
Repairing your 240Z Fuse Box.

A problem with early Z car electrical systems is the development of
resistance in the fuse box which can lead to melted spots in the
plastic fusebox, blown fuses, melted wires, and possible shorts in
the wiring harness. The areas that usually go first are the
circuits that carry the highest amperage, the lights and amp gauge,
because they experience the highest heat dissipation across the
resistance.

When the fuses blow, they only open at one end of the fuse, rather
than across the center of the fuse. The clip which holds the fuse
gets extremely hot, and melts the connection between the fuse
element and the end of the fuse. It is not caused by having too
much current in the circuit.

This condition is very easy to diagnose. Lift your ashtray/fuse box
cover, pull the clear plastic fuse box cover off, and briefly touch
the fuse clips with that particular circuit on for a few minutes or
so. If it's too hot to leave your fingertip on it, you have a
problem.

The fuse clips are brass, and the terminal rivets appear to be
steel. They are not soldered together, but depend upon metal to
metal contact. These are "dissimilar metals", and corrosion starts
working between the rivet head and the fuse clip. Corrosion =
resistance = heat, hence melting plastic and melting at the ends of
the fuse internally.

The fuse box can be replaced but it makes sense to try to repair
them because the cost of a new one is anywhere from $80-$100.

If the plastic is still in fair shape in the fuse box, one can fix
the problem by removing the fuse clips contacts by using a small
screw driver to depress the little barbs on the sides of the clips
and the push them out the back of the fusebox. This enables you to
clean and solder the clips to the rivets without melting the
plastic. Repairs to the plastic base can be made at this time using
JB Weld epoxy. JB Weld has a high melting temperature, much higher
then the original plastic. The tension that the fuse clips have is
also important, so carefully reform the clips so that they firmly
hold the fuse.

If the plastic base is in bad shape, you can "bypass" the fuse box
by using a 20 amp rated external fuse holder spliced into the
particular circuit. The external fuse holder can then be hidden
nicely behind the fuse box.

240Z Heater Problems

I have a 1970 240Z and the interior heater is starting to make me
mad. The heater will only work for about two minutes after the car
warms up, then it blows cold air. Is this a bad heater core or
what?

Some likely causes of your problem are:

1. The cables that come out of the back of the heater control
become disconnected at one or both ends. Or the clamp clips that
holds down the plastic part of the cable do not grip properly
causing it to slip back and forth, thus preventing the cable from
moving the various flaps that redirect hot and cold blower air.
Also make sure that none of your cable wires are crimped or broken.
It is not unusual to find the above problems on an older 240Z.

2. The heater core becomes plugged with corrosion and engine rust
deposits. Sometimes "back flushing" the heater core from the engine
firewall side with a garden hose (in the opposite direction of
normal water flow) will help.

3. If you can not get much flow through the core when back flushing
with the hose in either direction, and you get moisture
condensation on the inside of your windshield when you open the
heater core valve on a cold day or if you smell hot coolant in the
car, then it probably means that you have a bad heater core.

4. Finally, check your inlet valve to the heater core. Over time
they cease to work properly and may become stuck in a closed
position during the summer months. They are a bear to replace, so
use a new one if you do.

Tech Tip

What do the numbers and letters in a motor oil designation mean?

There are several different items encoded. There is a two-letter
code indicating the type of detergent package that the manufacturer
uses in the oil; this looks like SE,SF,CD or such. The S codes are
for gasoline engine applications; the C codes are for diesel engine
applications. The second letter is assigned in sequence as new
levels of protection are developed; thus SF is considered better
than SE, SE is considered better than SD, and so forth.

The more noticeable designation is the oil weight. This is either
a single number (e.g., 30 weight) or a pair of numbers separated by
the letter W (e.g., 10W30.) The latter type is much more commonly
used these days, and are the only type that most automobile
manufacturers specify in operators manuals. The first number in the
designation (10W) is the apparent viscosity of the oil when it is
cold; the W stands for `winter'. The second number (30) is the
viscosity of the oil when hot. There is a trick here; the oil
doesn't actually get thicker (turn from 10 weight to 30 weight) as
it gets hotter. What is actually happening is that when the oil is
cold, it has the viscosity of a cold 10 weight oil. As it gets
hotter, it doesn't get thin as fast as a 10W oil would; by the time
it is up to temperature, it has the viscosity of a hot 30 weight
oil.

Note that these numbers actually specify ranges of viscosities; not
all 10W oils have exactly the same viscosity when cold, and not all
30 weight oils have the same viscosity when hot. Note also that the
novel behavior of multi-grade oils is caused by additives, and it
has been reported that with the sole exception of Castrol GTX,
10W40 oils do not retain their multi-grade characteristics well
over time. 10W30, 15W40, and 20W50 oils work very well, though.

 

Engine Overheating Tips
1. Safety reminders before starting: Never open the radiator cap on a hot engine. Wear safety goggles to prevent antifreeze from splashing in your eyes. Keep your hands and clothing away from spinning fans.
Remember that some electric fans may operate after engine shutdown.

2. Check for obvious problems first. Loss of coolant because of a leak is probably the most common cause of overheating. Possible leak points include the hoses, the radiator, heater core, water pump,
thermostat housing, coolant reservoir, head gasket, freeze (or core) plugs, automatic transmission oil cooler, and cracks in the cylinder head(s) and block.

Checking for the presence of combustion products in the cooling system is the recommended procedure to determine a cracked head or block. If the leak is bad enough then bubbles will be visible in the radiator while the engine is running.. A simple compression check might also point to the same conclusion.

3. Make a careful visual inspection of the entire cooling system. Check belt tension and condition. A loose belt that slips may prevent the water pump from circulating coolant fast enough and/or the fan from
turning fast enough for proper cooling. The condition of the hoses should also be checked. It is recommended to replace the hoses if they are more than five years old. Sometimes a lower radiator
hose that has softened will collapse under a vacuum at high speed and restrict the flow of coolant from the radiator into the engine.

4. Attempt to better diagnose the problem. When a car overheats after only a few miles of driving, then suspect a thermostat stuck closed. If it gradually overheats only at idle suspect a faulty fan. If it
overheats gradually as it's being driven at steady speeds, suspect the water pump. If the engine overheating gets worse during higher speed operation, then a plugged radiator or a plugged cooling system are primary suspects.

5. Remove the radiator cap and pressure test the system at the radiator. A pressure test will reveal internal leaks such as seepage past the head gasket as well as cracks in the head or block. A leak free
system should hold 15 psi for at least two minutes or more. Start the engine and check to see if the system builds up adequate pressure as soon as the thermostat opens, and that the pressure continues to
build as you rev the engine.

It's important to pressure test the radiator cap because a weak cap (or one with too low a pressure rating for the application) will lower the coolant's boiling point and can allow coolant to escape from the
radiator.

6. Remove and check the thermostat. Severe overheating can often damage even a new thermostat. If the engine has overheated because of another problem, then the thermostat should be tested or
replaced before the engine is returned to service.

One way to check the thermostat is to start the engine and feel the upper radiator hose (or use an infrared non contact thermometer to read it's temperature). The hose should not feel uncomfortably hot
until the engine has warmed up and the thermostat opens. If the hose does not get hot, it means the thermostat is not opening.

Another way to test the thermostat is to remove it and place it into a pan of boiling water (it should open).  The exact opening temperature can be checked by using a thermometer.

If the thermostat needs to be replaced, install one with the same temperature rating as the original. Using a cooler thermostat in an attempt to "cure" a tendency to overheat can increase fuel and oil consumption, ring wear and emissions. On newer vehicles with computerized engine controls, the wrong thermostat can prevent the computer system from going into closed loop resulting in performance and emission problems because the engine fails to reach its normal operating temperature.

7. Overheating at idle can also be caused by insufficient airflow past the radiator. With mechanical fans, most overheating problems are caused by a faulty fan clutch although a missing fan shroud can reduce
the fan's cooling effectiveness, which may be enough to cause the engine to overheat in hot weather or when working hard. If a shroud is loose or was damaged and not replaced, it can be a contributor to
overheating. While you're inspecting the fit of the shroud, also look at the condition of the perimeter seals around the condenser and radiator.

Defective fan clutches are a common and often overlooked cause of overheating. The shear characteristics of the clutch fluid gradually deteriorates over time. Eventually slippage reaches the point
where effective cooling is no longer possible and overheating results. Look for a fan clutch that's running too slow when the engine is running hot. Typically, clutch fan speeds peak at around 2000 to 2200 rpm,
and you can use a photocell tachometer with some reflective tape to check for a slipping clutch condition. Rule-of-thumb is the life of a fan clutch is about the same as a water pump. If one needs to be
replaced, the other usually does too.

If the fan clutch shows signs of fluid leakage (oily streaks radiating outward from the hub of the clutch), spins freely with little or no resistance when the engine is off or wobbles when the fan is pushed in or out, it needs to be replaced.

With an electric cooling fan, check to see that the fan cycles on when the engine gets hot and when the air conditioner is on. If the fan fails to come on, check the fan motor wiring connections, relay and
temperature sensor. Try jumping the fan directly to the battery. If it runs, the problem is in the wiring, relay or sensor. If it fails to run, the fan motor is bad and needs replaced.

8. Check the water pump. Any wobble in the pump shaft or seepage would call for replacement. In some instances, although rare, a pump can cause an engine to overheat if the impeller vanes are badly eroded due to corrosion or if the impeller has come loose from the shaft. The wrong pump may also cause an engine to overheat. Some engines with serpentine drive belts require a special water pump that turns in the opposite direction of those used on the same engine with ordinary V-belts.

So how can you tell if the system is flowing enough coolant? One way is to install a special tester, such as Hickok's Radicool, in series with the upper radiator hose and compare the flow with the rate in the
manual (about 6 gallons per minute for engines less than 2 liters to more than 20 gallons per minute for big V8's).

If there's any reason to believe that the block may be plugged and could benefit from a flushing, then do it.

9. Check the radiator. The most common problems radiators fall prey to are clogging (both internal and external) and leaks. Dirt, bugs and debris can block air flow through the core and reduce the radiator's
ability to dissipate heat. Internal corrosion and an accumulation of deposits can likewise inhibit coolant circulation and reduce cooling. A good way to find clogs is to use an infrared thermometer to "scan" the
surface of the radiator for cold spots. If clogged, the radiator should be removed for cleaning or be replaced. Back flushing the cooling system and/or using chemical cleaners can remove rust and hard
water scale from the engine block, but do little to open up a clogged radiator.

If coolant flow is a question, you have to check the radiator separately. The most practical way is with a tapered cone rubber adapter that attaches to the radiator inlet neck and accepts a water hose. If you feed in a solid column of water and all that comes out the other neck is a trickle, then the radiator is obviously
plugged.

10. Other causes, although rarer, of overheating include:

Excessive exhaust back pressure. A clogged catalytic converter is usually the culprit here, but don't overlook the possibility of a crushed exhaust pipe. Check intake manifold vacuum at idle. If it reads low
and continues to drop as you slowly rev the engine then inspect the exhaust system.

Retarded or over advanced ignition timing (may also contribute to detonation and pre-ignition).

Overheated incoming air. On vehicles with a carburetor or throttle body injection, check the operation of the heated air intake system on the air cleaner. If the temperature control valve is stuck so only heated air from around the exhaust manifold is drawn into the air cleaner, it may contribute to detonation and/or overheating. Also check the heat riser valve for manifold heat on older V6 and V8 engines. If stuck shut, it may be overheating the intake manifold.

Overworking the engine. The cooling systems in many vehicles are marginal and have little excess capacity to handle the extra heat generated by towing or high speed mountain driving in hot weather.
A brake caliper that's sticking or a parking brake that isn't releasing may be making the engine work too hard as well.

11. When refilling the cooling system, be sure you get it completely full. Air pockets in the head(s), heater core and below the thermostat can interfere with proper coolant circulation and cooling. If the
cooling system has no bleeder valves to vent air, you may have to temporarily loosen a heater hose to get all the air out of the system. Remember never add coolant to a hot engine unless the engine is
running.

Pure water is unequivocally the best coolant. Use only the minimum amount of antifreeze required for your climate. But add a corrosion inhibitor such as Prestone's Super Anti-Rust.

Paint Care FAQ

What is Factory Applied (OEM) Paint?

This is the paint applied to a vehicle at the Original Equipment Manufacturer's (OEM) factory.

What is Fresh Paint?

This is a term used to describe "refinish paints" (paints used in automotive body shops) that have not fully cured.  Refinish paints are deemed fresh for 30 days after their application. Most paint manufacturers do not recommend applying a wax to fresh paint.

What is Cured Paint?

This refers to all automotive paints applied at the factory, and refinish paints that are more than 30 days old. Wax is recommended for application only to cured paints.

What is a Clear Coat Paint?

Clear coat paint refers to the clear (non-pigmented) top coat paint that is applied over a colored base coat paint, and is found on most vehicles built in recent years. Clear coat paint increases the vehicle's paint durability, gloss and resistance to harmful environmental effects. Most car care products that are recommended for use on clear coat paint are clearly marked "clear coat safe."

What is a Single Stage Paint?

Single stage paint refers to the pigmented, or colored, top coat paint applied to most older vehicles and some new vehicles. Single stage paints do not have a clear top coat. However, car care products that are marked "clear coat safe" may also be used on single stage paints.

What is Oxidation?

Oxidation is the dulling and/or hazy appearance of a vehicle's paint caused by weathering from outdoor exposure.  Correction requires the removal of the oxidized layer of paint by using a cleaner wax, polish, or rubbing compound, depending on the degree or severity of the oxidation.

What is "Orange Peel"?

"Orange peel" is a term representing the texture of a painted surface that has "hills and valleys" or bumps similar to the skin of an orange. Excessive orange peel is generally considered a paint condition defect.

What is a Swirl Mark?

A swirl mark is a curved, minor scratch left in the painted surface by a rubbing compound or a wool buffing pad. Swirl marks can be removed from the paint surface by using a polish or wax.

What are Polishes?

Polishes are specifically formulated blends of oils, solvents, water and minerals that are designed to remove minor paint surface imperfections such as fine scratches, light oxidation, water spots and swirl marks left from rubbing compounds.  Polishes may , or may not, contain waxes or silicones. Polishes create a deep, rich, swirl-free finish, and can be applied either by hand or machine.

What are Glazes?

A glaze is a polish that is safe for use on fresh paints. Glazes also have varying degrees of aggressiveness. Glazes, used either by hand or machine, will remove minor paint surface imperfections. It should be followed either by a wax on cured paint or by a hand glaze on fresh paint. Hand glaze does only minor polishing, and its primary use is to
enhance surface gloss and luster on fresh paints. It needs to be re-applied frequently until the paint is cured and can be waxed.

What is Silicone?

Silicone is a chemical polymer that has excellent water repellency and a very slippery feel. Silicones are commonly used in automotive waxes to enhance the application and ease of removal, and to increase gloss and durability.

What are Rubbing Compounds?

Rubbing compounds are specifically formulated suspensions of oils, solvents, water, and minerals produced in either a liquid or a paste construction. They are designed to remove paint surface imperfections such as scratches, oxidation, stains, and acid rain etching. Rubbing compounds can be applied either by hand or machine.

What are Waxes?

Waxes are uniquely formulated blends of wax, polymers, glossifiers and other ingredients that protect and produce a  durable, ultra-high gloss finish. Waxes make it easier to clean (wash/dry) the paint surface. Some waxes also serve as polishes, and are capable of removing minor paint imperfections.

What are Cleaner Waxes?

Cleaner waxes are wax/polish combinations. They contain mild abrasives that are capable of removing minor paint imperfections, as well as wax and other ingredients that produce a durable, high- gloss finish.

What is the Difference Between Rubbing Compounds and Cleaners?

There is little difference between rubbing compounds and cleaners that are designed to remove imperfections from a painted surface. They vary by the types of minerals (abrasives), mineral particle sizes and chemicals they contain, but they provide basically the same action. Both use an abrasive to remove imperfections in the paint, and both are made with varying degrees of aggressiveness.

How Often Should I Wax My Car?

There is no exact length of time that any wax will last. Variables such as the type, color and condition of the paint, the amount of exposure to outdoor elements, and the quality of the wax all affect how long it will last. Generally speaking, when the water beading and the finish appearance indicate that the wax is gone, you should re-apply the wax.

Why do I Need a Car Wash soap?

Car wash soaps are specially formulated to remove dirt, grime and soils commonly found on vehicle surfaces, while having a minimal affect on the wax finish. Many other soaps, such as dish washing detergents, are formulated to remove tougher soils like cooking oils and greases. These stronger soaps can attack a wax finish, reducing the overall life of the wax.

 

Repainting Interior Vinyl and Plastic Trim

How do you repaint the interior vinyl and plastic trim pieces in
your Z car?

Painting the interior vinyl and plastic trim in a Z is fairly easy.
There are two sources for the dye. If you don't have a paint gun,
then find SEM vinyl dye in spray cans at a good paint store. SEM is
the only way to go, and I have never found another product that
works as well or lasts so long. It also looks completely like the
factory finish. Please do not even consider any other brand.

Use "Satin Black" for the black interiors, and "Napa Red" for the
red interiors. The "Napa Red" is a precise match for the Datsun red
interior color. They also have ZX colors, too. SEM is about $7 a
can. and I use 4 to 6 cans for an entire interior on a 240Z.

If you have a paint gun (a door jamb gun is a good choice, or an
HVLP jamb gun is even better). Dupont has vinyl dye that is
comparable to SEM. It is about $20 for a quart, which will do one
car interior.

Preparation is everything! Here's the process:

1. Remove the seats and the carpet pieces.
2. Thoroughly vacuum out the interior.
3. Use low-lint paper towels to clean all the vinyl and plastic
interior pieces with a water based cleaner, such as soap & water,
ammonia, Mr Clean, Pineoil, etc., and let dry.
4. Wet wipe the surfaces with lacquer thinner. Not enamel reducer
or poly thinner, just cheap lacquer thinner. Wipe and scrub and
scrub. You will notice the vinyl and plastic getting soft. Stop
before you ruin the grain pattern! The theory behind the lacquer is
that it chemically softens the vinyl/plastic. When you apply the
dye, it soaks in much better.
5. Mask off all the unpainted items. I use "Big Gulp" bottoms taped
to the gauges.
6. Now shake your paint can. If you are using the Dupont dye, it is
ready to spray, without thinning.
7. Re-wipe the surfaces quickly with a very wet paper towel SOAKED
IN THINNER, and start fogging on the dye. It is very thin. You may
end up with 5-12 coats to get good heavy coverage. Let dry, and you
are done.

Note: Do not paint the seats, it will scrape off eventually.

Dupont also has a "textured" paint to match the texture of vinyl
tops. So it happens to look like vinyl when it is dry. I use it on
the sill plates of the 240Z's.

The stuff is very durable when dry. It does not exactly match the
Datsun sill plate vinyl, but it is a lot easier than trying to
recover the sill piece with contact cement and vinyl cloth. This
paint has to be applied with a non-HVLP gun (your normal old
fashioned gun is not HVLP). It's the air pressure that makes the
spiderwebs as it comes out, which then coagulate into the vinyl
texture. This coating can then be re-coated with black semi-gloss
vinyl dye to match the panels.

 

Tech Tip
What does it take to put the R200 differential in a '70-71 240Z?
Because the '72 and later Z cars moved the differential rearward about 1 3/8 inches, using the R200 in an '70 and '71 Z car requires some special consideration. BTW, this was a design change implemented by Nissan in 1972 to reduce the halfshaft angle and thus reduce vibration
and U-joint wear.

You will need:

1. The '72-'78 U-shaped rear suspension crossmember. This has a "curve" or bend in it to clear the larger R200 differential housing and also because you are actually moving the diff back a little.

2. A '72-'78 driveshaft. This is about 25mm longer in length. Note: the '72-'74 driveshaft
have replaceable U-joints, nice for maintenance.

3. The R200 "moustache bar". This supports the rear of the differential. The R200 bar has a curve in it and it is drilled for the wider mounting bolt pattern of the R200.

4. The R200 front rubber differential mount.

You can get everything off of 280Z that had an R200, i.e., a manual transmission 280Z. Your stub axles will bolt up OK, even though the R200 is slightly wider than your old R180.

Now, you will find out that the diff strap now comes directly over the R200 front rubber mount bolts. Since the nuts are on top, there's now not enough slack in the strap to bolt up.  The later Z cars moved the four bolts for the diff strap rearward.

So, you can remove the strap and use several turns of 3/16 inch steel cable threaded between the front rubber mount and the diff and then wrapped around the front diff crossmember to secure the diff. However, I recall talking to someone who used the 280Z diff strap, and
reversed the direction of the front rubber mount bolts so that the slim bolt head was on top and nuts on the bottom. This gave him enough "slack" in the strap.

Replacing Your Rear Wheel Bearings

Replacing rear wheel bearings on your '70-'78 Z car is something
you may have not yet undertaken, as it is not part of normal
maintenance and usually only needed on very high mileage Z cars.
Although some backyard mechanics may seem intimidated by the this
project, there's no reason that you can't accomplish it with some
guidance.

First, securely support the rear of the car and remove the rear
wheels. Now you don't have to remove the rear struts off the car.
Although arm room is limited and having the car on a lift will
help, I have accomplished this just with jackstands. This saves you
some time and you don't have to re-bleed the brakes. However, if
you're a first-timer, you are probably better off removing the rear
strut, as it gives you more access space.

Remove each strut by unbolting the rear halfshafts, the brake line,
the parking brake cable and the inner lower transverse link mount
from the car. There is no need to remove the transverse link arm
from the strut, as this can be more difficult than changing rear
bearings!

After removing the strut, you will see a large 27mm nut on the back
side of the stub axle. This nut has a "staked" or "peened" top,
which means it's top lip has been bent over on two flat surfaces on
the stub axle threads. This technique securely locks the nut in
place, preventing it from loosening, but it makes removal somewhat
difficult.

To remove the peened stub axle nut, first chisel all the way around
the top of the nut, not only just where it is flattened. Try to
bend the entire top lip of the nut away from the shaft. Do not try
to remove the nut until you have done this! This prevents any
damage to the stub axle shaft threads as the nut is unscrewed. In
addition, the peening greatly increases the amount of torque needed
to loosen the nut. Don't worry about damaging the nut, you'll
replace it anyway.

You can also us a high speed cutting wheel (even a Dremel) to cut
away the top of the nut--just go slowly and be careful not to cut
the stub axle threads where the nut has been peened over.

Now, the easiest method to loosen the nut is to use an air impact
wrench. However, if you don't happen to own one, then you will have
to resort to a 1/2 inch drive breaker bar (usually along with a
"cheater bar") and some arm muscle as the nut is tightened down
with some 200 foot-pounds of torque!

To keep the wheel/tire from rotating as you loosen/tighten the stub
axle nut: Go down to your local scrap iron yard and get a 1" by 1"
rectangular (hollow) metal bar about five feet long. Should cost
you about $5. Drill two holes in one end and bolt it to two of the
four holes in the flange that surrounds the stub axle nut. Leave
room for your 27mm socket.

If the nut is stubborn you can use a torch to heat up the nut. This
expands the nut a little and makes it easier to get the nut loose.

After the nut is [finally!] removed the stub axle can be removed
from the strut housing. The stub axle is pressed into place so it
must be driven out. There are two methods: "pushing" or "pulling".
Pulling requires using a hub puller that is bolted to the flange
where the wheel is mounted using lug nuts. A hub puller looks like
a large dent puller with a sliding weight and can be rented from a
tool rental place. You then use the sliding weight to pound the
stub axle out. It takes a lot of effort, but it is the safer method
as it will not damage the stub axle threads.

Pushing is easier, because you don't need to have access to a hub
puller. Using a large brass hammer the stub axle is hammered out
from the backside of the strut. Extreme care must be used so as to
not damage the threads of the stub axle! After removing the inner
splined flange piece, reverse the 27mm nut and re-thread it back on
the first several threads to protect the shaft and use a piece of
wood or hard plastic between the hammer and the top of the shaft.
Several strong blows will force the stub axle out of the strut.

Once the stub axle is has been removed from the strut, examine the
splines. Wear here is not unusual and this can cause a "clunking"
noise during gear shifts.

One of the rear axle bearings (there are two per side), the outer
one, will come out with the stub axle. To remove this bearing
requires what is called a "clamshaft puller". Again, you can rent
one, but I recommend taking the stub axle (along with a new
bearing) down to your local automotive machine shop and have them
remove the old bearing and put the new one on.

There is