I've read as many threads as I could find about 1993 cooling issues but I still have a couple of questions. I'm still waiting for my FSM to arrive so I can start diagnosing the problem. Anyway, here are the questions:

1. Is the temp sensor on the passenger side head below the spark plugs for the guage operation only and not the fans?
2. Is the temp sensor in the water pump sending the temp info to the control ECM ?
3. Is there any way to test the temp sensor that sends info to the ECM and turns on the fans?
4. Is there anyway to determine that the ECM is not sending the signal to the fan relay and turning it on?

Neither of my fans are coming on and my analog guage is creeping way to the right of center. I did the A/B short test and both fans come on. My AC is not working so I can't check to see if the secondary fan is working properly yet.

Any help would be appreciated.

 

First, ignore the analog guage and read the temperature from the digital guage. The analog guage is not linear and the only time you need to pay attention to it is when it is going much higher than usual.

Using the digital guage to show the temperature, I believe the first cooling fan turns on at 229 and the second at 239. That is how it works on a 1992.

 

This may provide a little info:
http://www.theherd.com/articles/lt1_cool.html

 

 

Thank you very much, I didn't even know I had a digital temp display. I'll run it again and see what temp readings are displayed. I'm replacing that temp sensor anyway since I'm replacing my water pump.

 

The PCM controls the electric fans. The way the factory programmed the PCM - the engine is going to run quite warm to hot in traffic. The fans don't come on at full speed till the coolant temp is 229 - 230 degrees. Only way to make the car run cooler is to get a chip burned with lower fan on settings, or to wire in a manual override switch that will allow the driver to manually turn the cooling fans on. The PCM relies on the colant temp sensor that live by the water pump.

So - First question - when youre just cruising down the freeway - what is the coolant temp - a LT1 / LT4 C4 with a good cooling system should stay in the 190's.

Second question - does the cooling temp (per the digital gauge) exceed the low 230's ever ???

Most of the cooling systme problems I've seen on C4's are related to either crud blocking cooling air to the radiator, or to anti-freeze that's been left in far far too long. So ... if there are issues - plan to pull the front radiator mount and pull the radiator out for cleaning, and do a full coolant flush (this means draining theradiator AND pulling the knock sensors to fully drain the engine block). The full flush is not a bad job, but it's not exactly what I'd call a fun job either, but you might be surprised about what ends up coming out when you do a full flush,,,,,,,

GOOD LUCK !!!

 

If you change the chip, the problem or effect is that the fans will always run due to the temperature of the engine and not cycle off. You lose control which I don’t like. Besides the primary fan should always be on with the A/C. We really are just talking about the secondary fan. But stuck in traffic when it is cold it will get hot and you will probably not have you’re A/C on. But all you have to do is get the secondary fan running.

In my opinion a manual switch is best to use for the secondary fan. You can always turn it on in traffic or when the temperature is getting to hot for your liking. I have had one for years and works great.