Easy thing first...thermostat. They have been known to go bad.

 

When a stat goes bad, can it open at a higher temp? I thought they just didn't open at all?

 

They could stick open, they could stay closed, they could hang up (part open) Anything mechanical will fail at some point, its just a matter of when. Take my 93 gran prix dd work car. 209,000 miles and going strong. 14 years old and runs like new, but one day even with the religious approach to oil changes she too will breakdown. Let's hope not until well into the 300,000's or maybe 400,000 I am going to drive her until the wheels fall off and then put the wheels back on. That car is my bread and butter. Ok back to topic, all mechanical things are prone to failure at one point or another. Check your Tstat and go from there. Good luck

 

I'm in agreement it is probably the t-stat. I'll let ya'll know how it goes.

Now for the million dollar question to dhdenny, who is that in your avatar?

 

Yeah I knew they could stick open (which is obviously not the case here) so I didn't really address it in that manner. By the sudden surge in cooling and heating, I thought it sounded like it was still opening at a higher temp. And in that case, I didn't think they could do that--just hang open or stick closed. I don't know, could be anything on these crazy fuel injected cars.

 

Her name is Jennifer Hurt. I wish she was my g/f. She's a Playboy model.