PontiacBonnevilleClub.com

96 SSEi, 204K Miles, Ambient Air temp of between 28-38F.

So, I have noticed that my temp guage tends to move a lot. Much more than any other car I have ever had. It bounces between 195 and about 210, but sometimes will go as high as 220. Never has gone above 220. This is a relatively quick movement and can be seen and discerned with the naked eye. It does a 195-210 sweep probably 16 times in 10 minutes.

It seems to go up when I accelerate, and goes down as I let off (or upon TCC Lockup) More boost seems to create more heat and a faster increase. Fans do come on at 220. at idle it sits at about 205.

Heat works fine...very hot. Coolant levels are good, haven't lost any that i can tell in 1000 miles. Upper Radiator hose gets hard as a rock and hot to the touch after car heats up. Does still have Dex in it, I will be flushing soon.

Should the temp guage move this much, please advise, I have to drive it home from work, about 50 miles, and I don't want to damage anything further.

Thanks!

My Cierra (3.1) used to do this when there would be a bubble in the cooling system.

Nothing has been done to the cooling system...what would cause this?

204K with dex-kill in it. Oh boy. Flush immediately

Getting flushed and new stat on thursday.

Do you know when your lower intake gaskets were changed? Dex-kill tends to destroy gaskets quicker.

Lowers never, uppers in 2010. No coolant in the oil or oil in the coolant. Hopefully the flush and stat will help, i really like the car but can't afford to put too much into it.

Did the bouncing just start or had it been going on for a while?

Let us know if the flush and new thermostat take care of the problem.
Otherwise if that doesn't work then I might lean towards the temp sensor. Its located underneath the thermostat housing, it might have a small heat shield around the connector.

The gauge panel in these cars is not necessarily the most accurate either.