GenVibe - Community for Pontiac Vibe Enthusiasts

Hi!
I'm new here and I'm still a newbie to the Vibe family. I have a 2004 AWD. I have a problem with the temp gauge and I believe it's the thermostat instead of the actual temp.
When I turn the car on, the temp is cold like it should be. I drive, it gets warm and goes past normal and straight to hot. But it's not overheating! It scared me but now it's just irritating because once it gets in that upper zone, the AC kicks off to avoid overheating the car. (This also happened when it was cold outside. The engine temp showed it was overheating but only cold air was blowing out of the vents ) It's a thousand degrees outside and my air conditioner is blowing hot air because the car thinks it's overheating.
Anyone have any ideas about this?

I would recommend checking the coolant level in the radiator by removing the cap when it is cool.
Don't go by the overflow bottle level.
A radiator with no coolant will blow cold air out of the heater even when the engine is overheating.
You can also use an infrared thermometer to check the temp at the thermostat housing, the hoses and the radiator.

You may/probably also have a bad thermostatic relief valve, aka 'thermostat'. Buy the Aisin one. It's underneath the intake manifold, and as that usually needs a new gasket as well, it's the easiest way to get to the thermostat rather than the convoluted "pull the belt, alternator, and wiring" to get to it.

So coolant first - if you fill it, cap it, do the recommended fill on the overflow reservoir, and then run it for a bit. When the temperature starts to rise, watch that coolant reservoir to see if it starts burping air. If so, when it get hot, shut it off, let it cool, pull the cap, and refill that and the reservoir again.