i installed an aluminium radiator and dual electric fans on my 75. evetything appears tobe fine (no leaks, fans turn on, etc). here is what i need some opinions on. the car calls for a 195 degree stat but they have 180 and 165 stats also. i have a 195 in it and car runs great the only thing being the fans never shut off and the motor does not overheat.

do you think it would be wise for me to install a lower degree stat so i don't over use the fans? and what degree stat would be suggested? thanks for any help.

I would install a 180 degree thermostat but that won't change your engine's operating temperature...it would simply make it take a bit longer to get there. If it normally runs at 195 degrees it will still run there. Besides...195 degrees aint't bad for a C3. Anything within about 200-210 degrees is considered normal and optimum for most operating conditions.

If it runs too cool it won't properly warm up and burn off contaminants and get full combustion.

If your fans won't turn off, maybe the sensor is set wrong. You can always install a manual switch.

If you say your car runs great...if it ain't broke, don't fix it! Or, in my case where I can't leave well enough alone..."If it ain't broke...fix it until it is!"

thanks bruce. i don't want to go too low but may change to a 180. fans sensor is set to turn on at 195 and off at 180. just don't want to overwork the fans. figuring if the water circulates earlier it might be enough to let the fans shut off for a bit.

Your 195 degree thermostat is maintaing that minimum operating temp so installing a 180 might help. As it is now, if your engine goes below 195 degrees, the thermostat closes and brings it back to that temp...it never gets a chance to allow the fans to shut off.

[QUOTE=Gunslinger]Your 195 degree thermostat is maintaing that minimum operating temp so installing a 180 might help. As it is now, if your engine goes below 195 degrees, the thermostat closes and brings it back to that temp...it never gets a chance to allow the fans to shut off.[/QUOTE]

sensor is mounted in radiator right under upper hose. i feel a lower temp stat will do the trick for a couple reasons. it will give the fans a break first. the confusing part is it will also allow the engine to run cooler. as bruce said too low is no good but if you look at some of the threads in here alot are adding additives to get the temp lower. i guess it's like a recipe, a guideline that you follo9w and adjust it to what works best for you.

i think it will be better also after i shut car off. i had the fans hooked up to run after car was shut off and they would run forever. i feel because the stat closed almost like forming a vacuum that the water would not circulate to get the cooler water to the sensor.  disconnected that for now as i am killing the battery. i don't think it is the sensor or the relay as when i tested it to begin with it worked fine.

also thinking about using a slightly lower pressure cap. new cap was supposed to be a 15 but was 16 so i put back the 15 that i had. will do it one step at a time and change the stat and then go from there and keep you posted.

thanks for your help.

I am not a big fan of the probe type sensors.  I prefer the in-head or in-manifold type.  I have my sensor in the intake.  It turns on at 200 and off at 190.  I have been driving the car in 100 degree weather and no cooling problems.  Don't forget to install all of the seals around the radiator and in the nose of the car.  The air has to be forced into the radiator because of the angled design. It isn't natural for the air to go that way. It will find the path of least resistance.  Do you have a solid shroud with the fans?  If not, there is a lot of dead area where the air is not being pulled across the cores.  I have a solid shroud with four 1 1/2 inch holes to reduce overpressure.      

[QUOTE=1969 L46]I am not a big fan of the probe type sensors.  I prefer the in-head or in-manifold type.  I have my sensor in the intake.  It turns on at 200 and off at 190.  I have been driving the car in 100 degree weather and no cooling problems.  Don't forget to install all of the seals around the radiator and in the nose of the car.  The air has to be forced into the radiator because of the angled design. It isn't natural for the air to go that way. It will find the path of least resistance.  Do you have a solid shroud with the fans?  If not, there is a lot of dead area where the air is not being pulled across the cores.  I have a solid shroud with four 1 1/2 inch holes to reduce overpressure.      [/QUOTE]

the sensor for this is the type you screw in. the connection for it is built into the radiator. only problem i am having right now is they don't shut down after it cools as i have them wired to stay on after key is off. if i cut the power to one fan they both stop. instead of running one wire to sensor i redid it to two separate wires. technically shouldn't make a difference but electric can be strange. i may change sensor to the block and see what happens but will see what happens with the lower stat and wiring change.
eddie208752007-08-26 11:02:06

With the sensor in the radiator, the fans should only run until the coolant drops below the cutoff temp.  Running time after you turn the key off should not be too long since you are only cooling the liquid in the radiator.  There may be a grounding problem with the sensor.  Most sensors are one wire.  Do you have a ground from the radiator to the radiator support?  That circuit has to be complete for the sensor to operate properly.  Just a stray thought.

spal suggested adding a ground wire as that was a problem with a lot of installations. when i wired the fans hooked a ground wire to the mounting bracket othe fan so the radiator has a graound wire directly attached. one wire should all that be needed but with two relays something could be screwy. after a bit if i pulled the fuse on one fan both would stop. i should mention here both fans have separate fuses and sepate power feeds. thanks for your input.