Any mechanic worth his salt will NEVER use stop-leak. It only makes whatever problem there is, worse. Also, beware of mechanics that replace a bunch of parts just to diagnose a problem. That is by far the least effective and most expensive approach.
Let's start with the overheating, since that's the most critical problem. You can get a compression tester, which measures the amount of cylinder compression of each individual cylinder. Generally, if you have two or more adjacent cylinders with very low compression, then you probably have a blown head gasket. If your compression is good, then the next step is to get a coolant pressure tester, which consists of a hand pump that you use to pressurize the entire cooling system to 15psi, and listen for hissing sounds, or obvious leaks. I was able to successfully use it to find an intake manifold leak, which only cost me $100 to fix. It will also tell you if your heater core is leaking.
Once you have taken care of any overheating problems, and any coolant loss (you should be able to drive for at least a year without having to add coolant), you can look at the A/C. I can't help you with that part, but keep in mind that there is no connection between the A/C and the cooling system.
Tuesday, September 25th, 2007 AT 6:08 PM