1990 3.1 Trans Sport Overheating

Ok, my temp gauge, even when the motor's cool, jumps to over 220 as soon as I start it, then proceeds to go into the red within 5 - 7 minutes of running. There "is" an oil leak, but I've been keeping the oil topped off religiously.

At the moment, the fan doesn't seem to be coming on, but it works when I put a jumper wire on it.

I'm thinking bad temp sending unit, bad gauge or both.

Thoughts? Anything else it could be?

Thanks!

-Sarge

Ok, just put in a new temp sending unit, but that didn't fix it... :headshake

Suggestions?

-Sarge

I just bought a 1991 Pontiac TS with the same engine/problem - temperature indicator starts from 1/4 and them climbs out of the normal zone. Engine works fine (not overheating) but this is very disturbing since I cannot tell what is the actual temperature of the engine.

Maybe someone could enlighten us about this issue.

I just bought a 1991 Pontiac TS with the same engine/problem - temperature indicator starts from 1/4 and them climbs out of the normal zone. Engine works fine (not overheating) but this is very disturbing since I cannot tell what is the actual temperature of the engine.

Maybe someone could enlighten us about this issue.

Yup! That's EXACTLY what mine's doing! It seems to be running ok, it's just that the gauge constantly crying "wolf!" is really creeping me out! :eek7:

Anyone?

-Sarge

No solution of my own, but several posts mentioned grounding problems making various parts of the instrument panel going haywire. At least, I'd try to install a separate ground strap between IP, body , engine block and battery negative. If it does not clear the problem, at least it will rule that option out ...
Another fact is several IP components and sensors work from a 5V power supply hidden somewhere. THis 5V can be measured at the throttle position sensor. I'd test for that too....
Keep us posted on findings.

probably air in the cooling system. I would recommend 'burping' the system. Put the front end up on ramps, engine cool. Open the radiator filler cap and fill to brim. Replace cap and then see if it solved it.

as suggested, "air" ...or stray exhaust gases into the cooling system, might be a problem. Blown head gasket is a "standard feature" of that engine. If that is the case, it will continually inject new "air" into the cooling system, whatever bleed you do.

About the "oil leak", is this an external leak (visible traces) of does it simply eat it ?

Also, specify what is "as soon as" as stated in your first post.....that is, does the needle jump up at key on..even before starting the engine ?..then how long for it to get into the red. The way you described it, I still suspect an electrical fault.