Hello. I am new to this forum and just looking for information on my 1988 C4. I was having some cooling issues and found out the heads were cracked so had those replaced with stock. Had head gaskets done, installed three core radiator with dual fans new water pump and thermostat. My baby is still reaching 260 on a short drive with low stop and go traffic. My fans are coming on at 185 my thermostat is stock. Any ideas why I would still be getting so hot? Thanks for reading.

 

How are you measuring it is reaching 260?

 

Digital display is reading 260

 

I'll assume that if you replaced the radiator it isn't blocked with debris. if the fans are properly coming on my first thought is the system isn't properly purged of air or thermostat isn't opening.

 

If the temp is 260 you should see coolant spitting into the overflow tank. Does the analog temp gage
confirm the 260 temp? If there is no sign of excessively heated coolant, other than the gage, try a new digital sensor.

 

Coolant was in the overflow at 260

 

Wow! Without more info (you have provided plenty) there may be exhaust gases being pumped into
the cooling system caused by a rupture in he new gaskets, or the new heads were not torqued to spec.

There is a test kit for testing exhaust gases in the coolant.

 

In such cases I always do a coolant system pressure check, and cap pressure check. Pump it up with the hand pump, to about 21PSI and see if it holds for a minute and stays above say 17 or 18psi. For the cap, make sure it holds 21PSI before it releases pressure. Cheap Amazon test kit should work fine. With lower system pressure, steam pockets can form and really raise the temps. If pressure check is good, perhaps check/replace the coolant temp sensor on the right side of the engine at the heads. Note that this is the hottest location on the engine, and the ECM and heavy duty fan option uses other locations.

Then, if the system hasn't been properly bled, there are some areas that will not let the air escape. If you're careful, you can bleed it at the steam relief hose which connects to the heating system on one end, and top of the manifold base on the other end. Another technique (that's more than a little sketchy), is to lift up the front of the car maybe a foot, start engine with the radiator cap removed (on cold engine), and crack open the throttle perhaps 2000-2500RPM, this creates a lot of pull from the radiator with the thermostat still closed, and also has the open cap at the highest point. Just don't hurt yourself trying to do it, and keep the coolant visible as it may pull it down excessively, just be careful when you let off the gas.

Also note that if it's running overly lean or with timing that's too retarded, the combustion isn't finished when the exhaust valve opens, and this will create excess heat in the heads and also exhaust manifold.