Anyone here have an intermittent overheating problem on their trucks? I can't figure this one out as it doesn't seem to be a problem with the electric fan's operation. I originally thought that the controller unit had crapped out, but there's just no method to the madness which would lead to this inference (the fan's operation seems to have no effect on the overheating issue). This leads me to believe that perhaps the valve which cycles the coolant between the engine and radiator has failed - does this sound reasonable? Has this happened to anyone else, and is this a part which needs regular maintenance? Could there be something else happening here which I might have missed? Thanx....

 

Sounds like the thermostat is sticking. I would check that first.
Edit:
I just saw you have a 1st gen SC. Maybee someone else with a SC will chime in.

 

You mean the thermostat? Yes, there is a good chance it is failing. Other possibilities are:

Clogged radiator core
HG leak (external on this motor - have you checked the recall?)
Radiator cap

Have you actually checked the fans by turning the knob all the way to - when it is hot? They should kick on for sure. I doubt this is the problem as the fans have very little to do with the normal operating temperature of the motor, the thermostat controls the majority of that. Keep us posted.

 

I had a thermostat where the support for the valve spring action was broken on one side. The thermostat still fuctioned but, only let about half of the coolant in. The results were it would run fine in city but on highway it would have a high tempeture. Like the guys said, start with the thermostat. Work your way up to the expensive repairs.

 

I have to guess thermostat as well on this one.
Any particular times when it does overheat? Any pattern there?

 

Could it be a short in your wiring? Are you getting steam or is your temp gauge getting hot?

 

Gulp... :pat:

Isn't that a sympton of the dreaded head gasket failure/recall? I recall my '90 experiencing water temp gauge spikes. I knew it was the head gasket when I found brown foam on the underside of my oil cap.

 

When I had this problem with my 22re it was a head gasket leak.

 

My '93 Camry 3.0L does this too. I think it is the thermostat but I can't get to it . Check and make sure the radiator cap is holding pressure and that the radiator/hoses aren't leaking. I found a old-age crack in my radiator, replaced it with a 2-core and it got better for a few months - but now I think it's the thermostat.

 

Well I don't like the sound of that! Hmm, what r any other symptoms of this HD problem that I can look for? I sure hope it's not that.

 

My temp guage is randomly spiking in hot stop and go situations. Here's what keeps me coming back to the fan though - if I'm at speed I don't have these problems. Moreover, I can bring the temp back down to a normal level if I can get the truck up to at least a constant 30mph. I'm pretty sure it has to be the controller unit, which for some reason has crapped out. Perhaps a sticking relay or some such thing....

 

It does sounds more like an air movement issue since the headgasket would cause it to happen at speed, too.