924Board.org

[CV924]

My 78 924 really heats up in stop and go traffic. Does this happen to anyone else? The temperature guage is in the red, but it goes back to normal once traffic starts moving again. Replaced the switch that turns on the cooling fan and I know it kicks in when in traffic cause I can hear it and the idle goes up to about 1200rpm.

Any ideas on what can be done to correct this or what the cause may be?

Thanks in advance.

[emoore924]

There are a couple of known fixes for this.

1) Change out, clean, rod out or otherwise fix radiator.

2) Replace thermo fan switch and thermostat with a matching kit of lower rated units. There used to be two kits that caused the fan to come on earlier/sooner. I can't remember the temps exactly but it went something like this....The one with the lower rating (fan on at 77c?) was generally considered to be too "cool", not letting the car warm up properly. The other (fan on at 84c?) is what I use in my car and I find it to be "just right" with the fan off at the lower white mark, on at the upper white mark. Note: You need to change the thermostat too for the cooler fan switch to work properly...

BTW, the up-n-down you describe is kind of normal, but the needle really should not get into the red.

[CMXXXI]

Flushing your radiator with the Zerex flush kit (or similar) if you can't/won't remove it to have it professionally cleaned out will probably help somewhat. As Emoore924 says, there are two ratings of fan switches and two ratings of thermostats. Switch to the lower rated set and that should solve your problem.

I have the higher temp rated parts in my car and I too will just about hit the red before things drop back off. I've started driving the 931 daily, now that temps are below 80F, and I note that the engine runs a lot cooler and stronger. With no A/C I have to pretty much park it in the summer, and drive it in the winter.
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'79 Eurospec 931

[gohim]

Actually there are three different temperature sets of thermostats and thermofan switches.

#1 is standard 195F. This is too hot to operate the car in warm/hot climates. Fan comes on at about 200F, and the temperature gauge goes into the last white mark and briefly into the red zone on hot days.

#2 is about 180F. The temperature gauge sets about the first white mark off the cold marker with this set. gets up to the 1/2 mark on hott days with the ac off. Run this set with RedLine "Water Wetter", you will like this.

#3 is about 165F. Never comes off the cold mark on the temperature gauge. Heater does not produce any heat, if you are in the snow. I tried this set once, got stuck at the top of the "Grapevine" (I5 in CA) in a light snow storm while waiting for a CHP group escort, and nearly froze with the ac temperature air coming from the heater.