Temp Gauge Problem

[Speed04]

So I've spent the past 2 weeks cruising the board searching and other stuff, but after trying just about everything I could find, I'm still having problems.

So about 2 weeks ago, the car overheated and died on me. Not real sure how it lost all the coolant, but it did. So we flushed the system and put a new 180* thermo in. Was still getting hot after that, so I went and bought the stuff and put a manual fan switch in. The switch works fine, but now I'm having another problem. The temp gauge will get up to about 230-240 then rather quickly drop down to about 200 and then over about a minute, climb back up to 240. It keeps doing this as long as the car is on. Then when I come home from being at school all day, it takes about 10 minutes, then jumps from about 180 up to 240 then starts floating back and forth like always.

Any suggestions? I've looked all over the place for leaks and can't find any. I'm running out of ideas and am about ready to take it to have someone look at it, but I'm just afraid it's gonna be something I could have done for like $20 and wind up paying someone to do it.

Thanks!

I forgot, I've got a '96, 3.8L camaro and I just had the radiator replaced like a year ago.

[Rob Bell]

Make sure the cooling system has been bled, the 3.8 has that bleeder screw up by the thermostat. If it's not that, maybe the headgasket went or the heads got warped. Check for a drop in coolant, maybe there is an internal leak.

[pontiac nino]

Check and see if you're fans turn on also, they're suppose to turn on when the a/c turns on.

[camaro_guy]

I have that same problem, when I drive around the city it sits around 212 and on the highway it can get up to around 240. I took it to a shop and they told me that my dying cat was causing it. Anyone ever hear of this happening?