Mike,
Where are you located?
Is your head shaved a lot?
I went through my 1.6L last summer and was able to get the
temp under control.
Here is a copy of the posting that I made. If you get a copy
of the Austrailian news letter (I forget the name), or the
TDROC Link, it was printed in both.
Peace,
Pat
- Support Habitat for Humanity, A "hand up", not a "hand out" -
Pat Horne, Network Manager, Shop Supervisor, Future planner
CS Dept, University of Texas, Austin, Tx. 78712 USA
voice (512)471-9730, fax (512)471-8885, horne@cs.utexas.edu
On Wed, 18 Jul 2001, datsunmike wrote:
> My car runs warm and I want to lower it. I did everything to the rad and
> everything else like Watter Wetter. I'm buying a bigger electric fan
> (recommendations?) and want to install an oil cooler.
>
> I'm thinkin of a 13 row Mocal with a sandwhich plate that has a built in
> thermo switch. Any idea if it will lower my temps? It will be mounted in
> front of the rad. I plan on using SS hoses with reusable fittings.
>
> Routing ideas for the hoses?
>
> Thanks,
> Mike
This whole process was taken on because of the difficulty that
I have experienced in getting my 1.6L, 67.5 Roadster to run in
the temperature range I had expected. Understand that I live
in central Texas, where it is not unusual for the air temperature
to run over 100 deg. in the summer.
First, a bit of "how the cooling system is supposed to work"
theory. The water in the engine pulls combustion heat out of
the cylinders and head. The thermostat controls the water flow
rate through the system to allow the engine to get up to operating
temperature more quickly and then control the temperature of the
engine once operating temperature is reached. The radiator gets
rid of some of the engine heat as the water flows through it. If
an engine produces more heat than the radiator can get rid of, the
engine temperature will rise. The amount of heat that the radiator
can get rid of is generally more than the engine can produce, thus
allowing the thermostat to control the engine temperature, rather
than the radiators dissipation controlling engine temperature. The
heat in the radiator is gotten rid of by airflow through the fins
on the radiator. A fan is required to move the air when the vehicle
is stopped, or traveling less than about 20MPH. This fan may be
either electric, or engine driven.
There are a few other items that can cause a car to run hot, or
appear to run hot. The temperature gauge can be off. The engine
timing can be too far advanced, causing extra heat generation in the
engine. The same goes for really high compression. Also, make sure
that the factory air scoop in front of and below the radiator is in
place and the radiator is not blocked. If the head has been shaved
too much the additional compression ratio can cause additional heat
to be developed.
I have experienced over temperature conditions on my roadster since
I bought it. I had the radiator cleaned, flushed the cooling system,
replaced the thermostat, and hoses. None of these changes produced
acceptable temperatures. The thermostat that I am now using is 180
degrees. The head has been cut farther than it should have been, so
that adds greatly to the heat generated in the engine.
I tried replacing the engine driven fan with an electric fan, but it
didn't help. (I tried both pusher and puller mounting, but the 14"
fan just couldn't keep up with the cooling requirements.) The fan
was on a thermostat that was set to turn on when the radiator inlet
temperature reached 180. On the road the temperature would still
run about 190, with it dropping slowly at stoplights. I finally
bypassed the fan thermostat and that allowed the fan to get a bit
more control over the heat, but not enough.
When I turn on the heater (fan on high) the engine temperature drops
about 10 degrees. This seems to say that the radiator is not
dissipating enough heat for whatever reason. It may be that the
radiator is crudded up, not enough heat transfer area, or the airflow
through the radiator may not be high enough. I first had the radiator
cleaned out, but that didn't help. I then removed the three row radiator
that was in the car when I bought it and replaced it with a high
efficiency radiator. This change brought the temperature down a few
degrees, but still not enough.
I tried adding an air dam under the radiator to cause more air to
flow through the radiator, rather than around it to increase the ram
effect, but it didn't help.
Next I replaced the water pump. The original one was from Auto Zone,
an auto part mass marketer. I installed a Nissan pump and the
temperature dropped another few degrees. (Ordinarily I wouldn't have
replaced the pump, but it sprung a leak at the rear plate gasket and
having a new pump on hand, I replaced the pump, rather than replacing
the gasket.)
I removed the electric fan and re-installed the engine driven 7 blade
fan with fan shroud and the temperature came down to about 180!
The temperature would stay at 180 solidly under all driving conditions
except when the air temperature was above about 104, a bottle of Redline
water wetter took care of that!
Water is a better heat conductor than antifreeze, so the lower
concentration of antifreeze the better the heat conduction. Redline
recommends an antifreeze concentration as low as 15%, so I set mine to
protect to +20 degrees (remember, I live in Texas and we don't see really
low temperatures here in the winter)! Antifreeze also keeps the engine
from forming rust in the cooling passages. Running too low a concentration
of antifreeze can cause more rust to form. Keep an eye on your cooling
system and flush it out if you find rust, then replace your antifreeze
with a higher concentration, but no more than 50%.
The only thing that I don't like about my current configuration is the
amount of noise that the fan makes. It reminds me of the fan noise from
my 240Z. I really liked the lower noise level of the electric fan! I
may try replacing the 7 blade fan with a 4 blade to see if it still
provides enough air movement while reducing the noise. I have been told
by a couple of different people that most engineers of fan cooling systems
don't put the fan completely inside the fan shroud, but leave it about half
way out of the shroud. I don't know if this is for additional cooling,
noise, or what, but I plan on doing some research to see what I can find out.
Here is another observation that may or may not help. There are any number
of different thermostat designs. I have one from Germany that has a much
larger opening than the US made thermostat. The larger opening will allow
more water to flow through the system. More water means a larger amount of
heat can be removed from the engine in a given length of time. Faster water
flow also means that the water passing through the radiator doesn't get cooled
as much by the radiator because the water does not spend as much time in the
radiator. I haven't tried the smaller opening thermostat, but I intend to as
soon as I have time
The readings that I reported were taken with a thermocouple, Omega Engineering
temperature to voltage converter and a digital volt meter. The thermocouple
was inserted into the upper radiator hose at the radiator.
Today it is 107 and the engine temperature sits steady at 180, whether I am
running 65 down the road, or sitting at a stop light.
Things are now MUCH cooler in Texas!
As a further note I swapped out the head for one that is close to stock
thickness and the engine temperature came down even more, so I suspect
that most of the cooling problems were caused by the high compression.
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