Ok so today I noticed that my car wAsnt blowing cold air when I had the heat on full blast and I looked down and my guage was showing my engine slowly getting hotter but as soon as I turned the heat off my engine heat went back to normal. I'm thinking the thermostat maybe needs to be replaced because it's sticking but I was wondering if anyone else has had the same problem or any insight on this situation before I go buy parts I don't need.

 

Sounds like the thermostat is stuck open and that is why as soon as you turn the heater on some of the heat gets dissipated and coolant levels will drop till you shut the heater off. Just get a new thermostat and you should be good. Had an evo VIII before and it got stuck closed while driving once, I had to pull over and pull the thermostat out in order for the engine not to overheat. It's an easy fix.

 

Cool that's what I figured just didn't want to buy one and end up not needing it because it's something else.

 

This doesn't make sense. You just said your WASN'T blowing cold air with heat on. Well, that's what its supposed to do.
And with the heater on, your coolant temp was going UP, getting hotter. This would only make sense if the tstat was stuck closed, but then you said it cooled off when you turned off the heater which doesn't make sense.


None of that makes sense. Try restating whats going on...

 

My car only over heated when I had the heat at full blast and when the heat was at full blast only cold air came out but when I turned the heat off the engine heat went back to normal.

 

That is completely counter intuitive, but does not point to the t-stat being stuck open. Did the car actually over heat (as in boil over coolant) or was it just the gauge reading hot? I would look into a temp sensor or something else, especially since these cars don't have a heater control valve, so turning the heater on/off has no effect on coolant flow.