We have a cooling issue on my brothers 94 Z28 with 193,000 miles...

The car consistently runs at 210-225 and you have to keep the defroster on to make the fans stay on. If you are at a stop with the defroster off the fans will go off and the temp will go all the way to the red. Also, sometimes the fans will come on even from a cold start...seems like sometimes they run all the time and other times when you need them they don't do anything. Reguardless of what the fans do the car goes up to 210-225 every time. The car heating up this much caused the radiator to crack a week and a half ago!!!

Things that have been replaced in the last 6 months to correct this issue:
160* Thermostat - twice
Water Pump
Radiator (today)

Car runs and drives fine and still makes great power. No normal signs of bad head gasket (coolant in oil, coolant leaking from heads, etc). It has been doing this since last summer and everything we have tried so far has not worked.

I hoped that it was just a bad radiator and replacing it today would fix the problem, but it did nothing...

So where do I go from here?

Let me know what you got.

Thanks,
Eric

 

did you replace it with a new one, or someone elses used one?

 

Check for air in your heads..bleed the crap out of youy system... air in the heads would cause your problem... keep me posted let me know how it goes...

 

Replaced the radiator with a used one that had 50000 miles on it. I know the guy and it cooled the car fine.

I bled the system very well and it was bled the times that other work was done. I think if that was the issue that it would have been sorted out sooner or later. I will open it up again tonight and see.

Thanks...keep the ideas coming,
Eric

 

It's normal for the engine to heat up to those temps (225) when the fans are not on and the car is not moving. Nothing wrong with that.

There is a problem though, that your fans don't come on after it goes past that. Perhaps the temp sensor in the water pump is bad. Use a scanner to tell what temp the PCM is seeing and if it is commanding the fans on at the proper temperature.
You can also use a meter to test the temp sensor and wiring. Info about testing and all about the cooling system can be found on my Tech Page.

 

Solved my own problem...

I hooked up a Scanmaster to the car which reads off the PCM...the PCM reads 218-226, which is because...apparently the car has a 160 stat in it, but it does not have a tune for the 160 stat...no big deal...but when my PCM is seeing 218-226 my gauge is seeing 245-260...

So apparently one of my temp sensors is screwed up.

Either...
The sensor going to the PCM is wrong causing the fans not to come on until the coolant is 260 degrees

Or...
The sensor going to the dash is wrong and the car is cooling just fine.

I am going to lean mroe toward number 2 since the car does not show any other signs of overheating.

So I will replace 1 or both coolant temp sensors and make sure the car gets tuned so the fans come on for the 160 stat.

Thanks guys,
Eric