I have an 03 Civic that has recently started overheating when the A/C is on and is still blowing cold air. I am due for an oil change and have approximately 185000 miles on it. When I turn the A/C off, the temp. gauge goes back down.

What could be my problem and is this an easy fix?

 

I had the same problem, replace the head gasket. This is not an easy fix, and I know you're going to go around trying to find "other things" like I did. Don't do it. Fix your head, don't throw money at random things. IF it is directly related to turning your a/c on and off it is most certainly your head gasket. The more times it goes above the half mark, the faster your car will permanently stop running.

 

Maugutus, any idea why that happens? Not saying you're wrong - that's a great piece of information to know about - just trying to understand the mechanism that causes it.

 

There is a thread on this.

https://honda-tech.com/forums/showth...889523&page=12

 

Your engines cooling system has to be efficient, when load is placed on the engine the pistons work harder, generating more heat. If your cooling system is not up to par it just wont dissipate the heat properly. You have alternator, power steering, water pump, and camshaft loads on your engine constantly. Adding an A/C load to a car with a failing head gasket will push it slightly over its capacity and begin to overheat the car slowly. By contrast, a stuck thermostat, no coolant, bad hose, or bad radiator situation will cause rapid overheating. Even one overheat situation can (above the half mark) can cause the head to warp.

When my car overheating it had a leaking head gasket. There was exhaust in the radiator, you could see the bubbles and smell it. Eventually it blew the radiator. I replaced that, and replaced all of the gaskets and o rings, and got the head machined. Going on 3200 miles with ice cold A/C.

Good luck.