Datsun Cooling Tips for the Roadster and 510 Sedans.
by Thomas Walter c 1996, 1992
last updated 1 NOV 96
Originally Titled: KEEP YOUR COOL, on the road to Mount Shasta!
Time to start thinking about the warmer months ahead, and plan for
that drive to Mt Shasta for the annual meet. Let's make it a 50 roadster
caravan from Portland!
Is the temperature sensor working?
Is your 2000 missing a ground connection? The temperature sender is
"sand- witched" between two gaskets, which originally has small
staples in them to provide the ground path for the sender. Most
after-market gaskets do not have the staple in them to provide the
necessary grounding. Ma Roadster recommends using a hose clamp to hold
a grounded wire firmly against the sender. The wire must be long
enough to attach to the frame grounding point, and not get caught on
anything.
Is your radiator clean?
I had my radiator roded out for $55.00, Cheap insurance on newly rebuilt
engine! If you are not sure of the condition, or age, of your radiator;
have it roded out!
How much pressure should you run?
Original radiator's should not be subjected to pressure over 4 PSI!
Nissan factory caps are designed for seven PSI. Thankfully early Jaguar's,
have the correct dimensions, and a pressure rating of four PSI (Stant Part
number R8 or SP8 [safety cap]; Gates Part number 31324 or 31504 [safety
cap].
Higher pressure will cause the stock radiator to bow outward, from the
middle.
What temperature thermostat?
You should always run a thermostat! The 1600 and 2000 engines generally
run best with an 160 degree thermostat. It is normal for the coolant to
reach 200 degrees on a hard run up a hill, but there is no reason for your
roadster to overheat!
L series engines typically prefer an engine temperature of 195 degrees.
------------- TABLE 1 --------------------------------------------------
Boiling point of WATER under pressure.
PSI deg. C deg. F
atm. 100 212
5 110 230
10 116 240
15 122 252
Running a mixture of 50% Antifreeze/50% Water will give you a higher
boiling point, but not exceed 50% antifreeze
(source: CRC Handbook of Chemistry and Physics, Vol 66, on page D-190)
-------------------------------------------------------------------------
For those modified souls;
I would recommend a custom three row core if you're running a modified L-18
engine as they prefer a engine temperature of 195 degree, and the L series
engines run a 14 psi pressure cap. Does anyone have any experience, good or
bad, with the roadster heater core at the higher pressure? Once again,
never run a L, or Z, series engine without a thermostat! IF you leave it
out you are asking for longer warm up times, and for severe OVERHEATING
in the back of the engine (#4 cylinder) as the water will tend to cavitate
in that area leaving an air pocket, and no cooling! Even the BRE Team
learned this early on, placing a restricter in the water outlet to slow the
water flow down.
heater or no heater?
Do not run a straight hose between the heater outlet and inlet on the
engine either! If you do not use a heater, cap the outlet and inlet.
Normally the path would flow through the heater core, returning cooled
coolant to the engine, but to "short circuit" this will cause more
problems than it solves!
On the 68-70 Roadsters there is a small "question mark" shaped hose
under the dash. When I was checking it, the hose was too brittle,
mine broke! A few quarts of coolant dumped into the car! Well, the
car needed new carpets! The original hose is not available,however,
a part from a late model ZX works fine, after being trimmed.
Part # 27183-P6500. [The original valve & hose came as a unit:
part # 27090-25900].
The heater hoses that run under the dash can be a source of irritation.
To removed the clamp from my heater outlet, I had to remove the center
console and radio console! A lot of work to get at one clamp! Worse yet was
the old hose was so brittle and old, pieces of it remained on the heater
tube.
Three hours, and lots of elbow grease, later I was able to clean enough
off with a piece of course emery paper.
For the heater hoses, I used "GoodYear 5/8" red heater hose". Baxters
Auto Parts carries the hose, but at a premium cost compared to the standard
black hose. I would have preferred the appearance of the black hose, but
the red one carries a "life time warranty". Of course if the hose fails,
they`ll replace it but not your $2500 2000 engine!
To ease the job of replacing the heater hose, you need to clean the old
heater fittings. Steel wool, 00 size, works fine to clean the old fittings.
A light coat of vasoline, or white grease, will assist in sliding the hose
on. Another trick is to cut a small (1/8") bevel on the inside of the hose,
which allows it to slide on easier!
Where the heater hose passes through the firewall, make sure the grommet
is in place. If a grommet is not in place, then a small piece of clear
tubing, or fuel line, can be split lengthwise and wrapped around the edge
of the sheet metal to prevent it from cutting into the hose.
If the two heaters hoses rub against each other, try placing a piece of
hose that has been split lengthwise around one of the heater hoses, and
secure with a cable tie.
Fan Clutch?
If your 68-70 Roadster has an original fan clutch, it should be replaced!
The original design used a bi-metallic "Q" spring. The bi-metallic strip
would expand when hot, locking an asbestos pad against the fan pulley.
The spring's asbestos lining tended to fail after a few years of use,
letting the fan spin freely, causing the engine to overheat in traffic.
The fan isn't need at higher freeway speeds, but more for around town use
at speeds lower than 20 mph.
There was a recall in '71, or so, to replace the defective fan clutches.
So some where caught early on, but not all owners were notified.
The recall consisted of replacing the original fan clutch with a a solid
aluminum spacer (part # 99991-10010 on my '68 2000).
Fan/shroud?
The shroud should aways be refitted, as it helps improve the air flow,
keeping your roadster cool in summer traffic.
The fan on my '68 2000 is a 7 bladed plastic one, which isn't necessary.
A four bladed fan will work just a well, with less noise and drag (Tip from
Rallye Roadster's catalog). I have seen a '68 2000 using a TOYOTA bolt on
fan clutch, but I have no further information of what model Toyota the fan
clutch was from. As Datsun L-engine owners have noticed, the fan clutch is
part of the water pump, making it an expensive replacement item, and not
adaptable to the R16 and U20 engined roadsters.
I have seen some roadsters fitted with an electric fan IN FRONT of
the radiator. If you have done this, I would appreciate an article for a
follow up on the Roadsters Cooling System!
How much "Antifreeze" to run?
Refill with 50% antifreeze and 50% distilled water.
A 1600 holds approximately 7 quarts of fluid, 2000 holds approximately
8 quarts. You'll never be able to get this much into the system, as it
never drains completely. Start off pouring in 2 quarts antifreeze, 2 quarts
water. Now mix half water and half antifreeze into an empty jug, label it
50/50 mixture, and use this to top the rest of the system.
------------------------------------------------------------------------
Properities of Water Vs. Antifreeze
Liquid thermal conductivity: Boiling Point in C
W/(m*K) in C (atm = 0 psig)
water 0.60 100 212 F
23% antifreeze (by vol) 0.53 101 214
38% " 0.45 103 217
54% " 0.40 105 221
pure(!) ethylene-glycol 0.25 197 386 !
---------------------------- TABLE 2 -----------------------------------
Table 2 shows the properities of Water Vs. Antifreeze. While Pure anti
freeze looks like it will prevent your roadster from overheating, don't
believe it. Even with 1% water, the boiling point is radically lower,
plus pure ethylene-glycol has a lower thermal conductivity than
water, meaning you would need a larger radiator!
Pressure testing:
All done, hoses in place, time to "pressure test" the cooling system.
Do this with the engine off, and cool. A simple pressure tester can be
made from pressure gauge (10 psi max is fine - most "vacuum gauges"
also show the pressure readings), an old bicycle tube, and bicycle pump.
Cut the valve off the bicycle tube, stuffing it into a hose, and clamping
it. Attach the other end to a "T" fitting, which connects to the pressure
gauge, and the remaining side is connected, via a rubber tube, to the
fitting on the radiator (after disconnecting the line to the overflow tank).
With the pump and gauge fitted, replace the radiator cap(on the radiator
of the 2000; on the head on 1600's. SLOWLY start pumping to pressurize
the system. A small hand pump works fine... do not use an air compressor
to do this! Five pounds of pressure is all you need to find a leak.
The top radiator hose will become firm with pressure, and should be able
to hold pressure for at least five minutes.
If there is a leak, it is much easier to hear with the engine off!
A piece of rubber tubing, with one end placed near your ear will allow
you to easily hear any leaks in the system.
UPDATE:
November 1996: Since writing this, I have found it still holds true.
I have finally purchased a MAC PRESSURE Tester, nice kit so I can
test radiator and pressure caps on my various Datsun's.
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