Temp gauge going funky, Updated! Changed Thermostat but still does the same prob Options

[reko]

As i was driving on the highway on friday night i noticed that my temp gauge was almost at cold which isnt normal for a sunny summer day.

After rolling for 10mins, it went to normal temp. but started to go slowly from normal to cold back and forth 4 to 5 times after what it stays at the first 1/4.

It did it only once, but then on the next day, it did it 2 times and went back to normal.

Nothing happened yesterday, but still, i dont really like this.

I'm thinking thermostat, but who knows?

Is it bad? I mean I went to school today (which is about 20kms from my house)... should I change that tonight?

**UPDATE**
25/08/08: Changed changed the thermostat... The shaft bent so it was stuck open so I just put one for Camry since the one for Celica 2.2L didnt fit (dont know why but anyway....) Still does the same problem as before... temp gauge isnt stable...

So what's next?
Water pump maybe

This post has been edited by reko: Aug 25, 2008 - 5:47 PM

[reko]

as i was going to school temp got really hot... almost in the red zone (I'd say it was missing 1/8 inch) so i turned my heater on and it went back to really cold (below first 1/4).

When i came back, i didnt put the heater on and it stayed in the first 1/4

I dont have school tomorrow so it would be the best time to fix this. Any ideas? Could it be the fact that its the thermostat for a Camry and its not the same size has the one for the celica the dude sold me at first??

I forgot to mention that im at 195 000 kms so that means timing belt and water pump in 5000 kms

This post has been edited by reko: Aug 25, 2008 - 5:45 PM