Yukon temp guage fluctuating

bailj · December 27, 2004

The temperature gauge in my '99 Yukon is fluctuating considerably. At Hwy. speeds up to just about 210, then down to 2 lines below (what I would guess is about 190/195). It stays there for a few seconds and then climbs again and continuously does this. I recently had the gasket in the manifol replaced which was leaking coolant, and they installed a new thermostat at that time. Took it home, gasket and leak was fixed but now the thermo climbs up and down continuously. I took it back in and was told it was diganosed as a sticking thermostat which was replaced. Took it home, same thing is still happening. Coolant is full/topped off and I just replced the sending unit that is right near the exuast manifold since it seemed logical that it could be this which did not fix it. Also, no bubbles in the coolant/radiator which might point to a head gasket issue. Fan is mechanical and turning fine so no problem there. There is also another temp sedning unit right near the thermo but havent puleed that one yet since it sends a signal to the computer and not the gauge. Is it possible to have two brand new thermo's in a row be bad? Anyone have any suggestions? Help!

jerrynsr · January 5, 2005

This sounds like the same problem I had with my Silverado.

I bet the intake manifold gasket job failed.

Check your intake manifold gasket. GM makes them out of plastic and they tend to fail.

I had mine replaced with a high performance metal/cork gasket. No leaks.

The temperature gauge in my '99 Yukon is fluctuating considerably. At Hwy. speeds up to just about 210, then down to 2 lines below (what I would guess is about 190/195). It stays there for a few seconds and then climbs again and continuously does this. I recently had the gasket in the manifol replaced which was leaking coolant, and they installed a new thermostat at that time. Took it home, gasket and leak was fixed but now the thermo climbs up and down continuously. I took it back in and was told it was diganosed as a sticking thermostat which was replaced. Took it home, same thing is still happening. Coolant is full/topped off and I just replced the sending unit that is right near the exuast manifold since it seemed logical that it could be this which did not fix it. Also, no bubbles in the coolant/radiator which might point to a head gasket issue. Fan is mechanical and turning fine so no problem there. There is also another temp sedning unit right near the thermo but havent puleed that one yet since it sends a signal to the computer and not the gauge. Is it possible to have two brand new thermo's in a row be bad? Anyone have any suggestions? Help!

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