924Board.org

[coup85]

I've been dealing with some issues with the cooling system in my car. I had to fix a bad hose, replace the thermostat and the water pump, and completely purge the cooling system –including some radiator cleaner–. After doing all this, the main problem with the temperature fluctuations in the car was resolved, it still goes a little down on the highway but always on the main limits, but still goes up on traffic, sometimes over the limit.

However, a new issue has popped up. When I turn off the engine, the fan continue running for a bit and then stop and if I start the car again, the temperature gauge shows that the engine has overheated, and sometimes liquid even spills out of the overflow tube.

I'm not sure what to do next. Should I check the temperature switch of the radiator? The ballast resistor maybe?
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924 - 79'

[morghen]

I presume that the coolant temp stays where it should stay when driving.
Higher temperature shown on the dash after re-starting a hot engine in hot weather is normal, mine always did that thing where even though the fan would run for a while, if restarted a few min after shutdown in August or July, the temp gauge would show its hotter but only for a few seconds until the coolant is recirculated.

If coolant comes out in those situations, you can have one or more of the following: cap isnt sealing, coolant tank is cracked (they all are by now), you have air in the system.
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Supercharger and EFI kits
https://www.the924.com

[coup85]

Thanks. The system is already purged and there are no leaks on the tank –or at any other part I'm aware of–, I'll try with the old cap to see if there are any changes but the seal of the new one looks good.

Sadly I went out for a ride and while on the road the temperature was fine, in slow traffic, it goes up. I tried to keep the engine going when I parked to see if the temperature went down, but it didn't.
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924 - 79'

[Raize]

You could check the temperature rating for your radiator switch, you might have one that's too high. There are a few versions. Should be physically marked on the hex, hopefully in a direction you can see.

You don't need to check ballast resistor, fan is coming on with the car stopped so that's working as intended.

You might want to check the fan relay, you can check this simply by turning the ignition on while the fan is running after turning the car off, and see if the fan speed increases. It should increase significantly.

Radiator caps are suspect, I had about five used ones and none of them would seal. Probably buy a new one if it's never been replaced.

It's normal to lose some coolant after filling it, it needs to find the equilibrium point where it's not opening the pressure relief valve on the radiator cap when it's as warm as it gets.

You might also have a faulty multi-gauge that reads about 1/3 too high sometimes like mine. If I knew why, I would have fixed it

[coup85]

That's really helpful, I'll definitely check all those. The problem with both the fan and the radiator is the previous owner updated them and I'm not 100% sure of the specs, nor of the switch that I suppose might been updated with the rest too.
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924 - 79'

[coup85]

Quick update: It was the fan relay. Now I can see a significant increase in the fan speed when I turn the ignition.

Thanks a lot!!!
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924 - 79'