I have a 2002 Sunfire GT. Lately, i've noticed that when my car is idling/driving and especially when my heat/AC is on....i notice my temperature level increase but a few lines over the half way mark. Usually to get this down again, i turn the heat/ac off and it drops down a bit. Is this cause for concern? I have never noticed it went past the halfway mark before, until recently. I'm not very automotive knowledgeable. Thanks for any help.
I would check your coolant level and see if your radiator is operating correctly. A car's thermostat maintains the engine's lowest opertaing temperature and wouldn't have anything to do with overheating unless it was stuck closed. In that case your car would overheat quickly. If it were stuck open then car would probably run rich as the engine wouldn't heat up and never enter the closed loop for the PCM. If you're just noticing an increase in engine temp, especially when the engine is placed under an extra load, I would think the cooling system isn't operating as efficiently. Cooling system components are; thermostat, radiator, water pump, radiator hoses, heater core hoses, heater core, cooling fan (either electric, engine driven or both), fan shrouds and coolant. Before you just add water to your radiator or expansion tank you should know that a 50/50 mix of distilled water to antfreeze is recommended.
I just found out that Dexcool is causing a problem. The water in the coolant solution is boiling out and leaving the antifreeze behind. So you could definately have low coolant. There is an additive in Dexcool that is attacking the rubber seals of your radiator pressure cap and is allowing the steam to bleed out. Get your radiator pressure cap looked at!
I added Coolant immediately when i noticed the problem....didn't seem to help. Added some green coolant. Forget what it's called. Thanks for the reply. I'm not automotive literate at all...had to read the car manual just to find out where the coolant tank was lol