Erratic temperature gauge

[jpfletch1]

I have been breaking in my car this weekend. It has a 482 aluminum engine. I am puzzled by how erratic the temperature gauge is. When going down the freeway at 2200 rpm in fifth gear the temperature gauge will be at 90°C and then jump 110°C and then fall back. I can't figure out why the temperature would change back and forth so rapidly. It seems like the gauge should gradually move up and gradually move down. Any ideas?

[wtm442]

Sticking gauge if its mechanical or large air pocket in motor.

While driving, tap the gauge and see if the pointer jumps.

[sllib]

If it's electrical check to make sure the threads aren't gunked up with tape or thread sealer. You need a path to ground.
Bill Stradtner

[392cobra]

Thread sealant shoudn't be used on the electrical sender that goes into the intake manifold ?

[Michael C Henry]

Watch out for a pluggeg thermostat by pass. that little fost from the intake manifold to the rear top center of the coolant pump. It keeps coolant circulating..

[kmarccoco]

low coolant? air pocket? try filling coolant with front end on incline.

[392cobra]

Originally Posted by 392cobra

Thread sealant shoudn't be used on the electrical sender that goes into the intake manifold ???

TTT

How about sealant in regards to an electric oil pressure sender too ???

[Zoom This]

Could be your themostat. When I watch my temp gauge it will fluctuate very slowly between 75 and 78, back and forth while driving on the freeway. In my case, it's just the thermostat closing and reopening just a little.