Temp gauge acting weird

I have a 91 Sundance, posted about it here before. Just got it a few weeks
ago. I had some cooling and heating issues, got those fixed. The problem i
have now is the Stock temperature gauge. When i first start it up, after
about 5 or 10 minutes the gauge goes all the way to hot, stays there a few
minutes, drops back to almost cold. As time and miles pass, it keeps doing
this, but the swing isnt as severe and it eventually settles just short of
the middle of the gauge. I've gotten out and checked the engine when it said
it was hot, by feeling the cap, hoses, etc. Nothing that i would call not
normal. So do i have a gauge/sensor problem? I cant imagine temperature
swings being that rapid.

 

Could be air in the system, or the thermostat not opening when it
should.

-Kirk Matheson

 

i just put a new thermostat in a couple weeks ago, and i thought i got all
the air out, maybe i didn't. I'll try that again. I do have an aftermarket
gauge i am gonna put in anyway

 

Two things, the head gasket is blown causing combustion gases to enter the
cooling system and causing an air pocket at the thermostat, this will cause
the thermostat to take a long time to open because it is not rsesting in the
coolant, the steam acually opens it.
Once it is open you may not have this problem untill the next cold start up.

Or your heater core is partially stopped up causing lack of circulation in
the head. Do you have heat coming thru the vents?
Glenn Beasley
Chrysler Tech

 

Yes I have SOME heat, but its not that great. I was wondering about the
heater core.

 

Take and bypass the heater core, connect the hoses together at the firewall
and drive it, see if the problem is gone, if it is... i think you know the
answer to your fix

Glenn Beasley
Chrysler Tech

 

I had similar problem with a cracked head gasket