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Fluctuating temp. guage


bailj
12-27-2004, 02:31 PM
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!

GMMerlin
12-27-2004, 07:32 PM
If your guage is moving between 195 and 210, I really wouldn't worry to much.
The gauge on your dash is more or less an indicator instead of a true read gauge.
What is happening is as your truck engine heats up, the temp will climb to above the regulated temp of 195..usually around 210 then when the thermostat opens, the temp will cool down to about 190/195..this is considered normal operating temperature.
If you said that the temp would climb to 240-250 then I would say you may have a sticking thermostat or maybe the fan clutch is getting weak.
I have seen many peole complain about this..usually right after a repair to the cooling system was done....usually because they were accustomed to the improper operation of the gauge caused by the faulty cooling system.

WEF
12-27-2004, 09:34 PM
Did all this start after the manifold gasket replacement? Maybe it has air pockets in the coolant. See if there is a small plug around the thermostat housing to bleed the air. The LT1 engine has this and it is necessary on that engine.

2kflhr
12-30-2004, 10:42 PM
Did all this start after the manifold gasket replacement? Maybe it has air pockets in the coolant. See if there is a small plug around the thermostat housing to bleed the air. The LT1 engine has this and it is necessary on that engine.

The LT-1 engine had a reverse flow coolant system.

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