1988 Chevy overheating

[Chris Ziegler]

Hello I am new to the forum. Would like to know what is causing my 350 engine to over heat? It is a problem that has been going on for some time. I have replaced the radiator, sending unit, and have tried several thermostats. The truck has never boild over but the temp gauge shows it is running at or about 230 F to about 240 F. The temp gauge jumps when it goes up sometimes by 20 degrees ahalf second at a time, and goes back down that way as well. It doesn't loose any coolant or water, always full.

[horse482]

Have you used a mechainical temp guage or other type of thermometer to check to see what temp you truck is actually running at? It is possible that the guage in your dash is reading incorrectly. Once you find out if your guage is reading correctly or not then if so you can start trouble shooting more. Hope this helps.

[2000CAYukon]

Does it run hot sitting in traffic or when you going down the highway? Or both?

A bad fan clutch can cause it to overheat in stop and go traffic or at low speeds.

//2000CAYukon

[Chris Ziegler]

No i have not tried a diffrent gauge. This I will do. Thanks

[Chris Ziegler]

Originally Posted by Chris Ziegler

No i have not tried a diffrent gauge. This I will do. Thanks

It runs hot sitting at a stop and driving it.

[Chris Ziegler]

I was wondering how you check your clutch fan to see if it is bad.

[2000CAYukon]

Originally Posted by Chris Ziegler

I was wondering how you check your clutch fan to see if it is bad.

Engine off, spin the fan. It should have some drag to it. If it spins freely, the clutch is bad.

The fan clutch disengages at highway speeds, so if it is overheating at highway speeds, it may not be the fan clutch.

Also, take a close look at the a/c condensor in front of the radiator. If it is clogged, air may not be flowing thru the radiator and you will overheat.

//2000CAYukon

[Chris Ziegler]

Originally Posted by 2000CAYukon

Engine off, spin the fan. It should have some drag to it. If it spins freely, the clutch is bad.

The fan clutch disengages at highway speeds, so if it is overheating at highway speeds, it may not be the fan clutch.

Also, take a close look at the a/c condensor in front of the radiator. If it is clogged, air may not be flowing thru the radiator and you will overheat.

//2000CAYukon

Thanks Yukon for the info