I am having the weirdest problem ever, My 2004 6speed 70,000 miles, is leaking coolant, not all the time..
The thing is whenever it gets hot over here in Arizona, only when the A/C is on the car starts leaking coolant from beneath the car i think somewhere near the radiator, for some reason it never leaks unless i turn the a/c on, then the car starts overheating from the guage, and when i turn off the car, the water starts leaking from beneath the car, when i reload the coolant tank with water i start the car, it starts okay with no problems and it never overheats nor leaks water. Seems the problem is whenever i turn on the A/C and when the car overheats, the A/C starts blowing hot air, then some cold air then back to hot air, then it leaks whenever i turn off the car..
Any expert can help me out???
please i really need the help am about to burst out...

 

I am having the same problem with my 2005 AT. I did notice that the radiator cap does not have a good seal and it looks like the coolant is leaking from there. I am going to change that out this weekend. Please let me know if you find more information to fix the problem.

 

This has been happening to my car but now it's gotten to the point where it leaks even when the AC is off. Yours may eventually get to this point.

Someone told me it might be from the belt that runs the water pump as well as the AC. This person said that if the AC and the water pump run off the same belt, then when the AC is on, it can create additional strain on the water pump. IF the water pump is already starting to fail, then the additional strain will cause a slow, gradual leak that gets worse and worse until the water pump fails completely.

Wait for the real experts to chime in on this thread. I'm curious about a more definitive answer as well.