I have been losing coolant at least once every two weeks or so and have to put pretty much a gallon back in and no one can find where it would be leaking, car gets hot or overheats, does cool down if I put ac on but ac does not work very well as it is.
If putting on the ac cools it down, maybe your electric cooling fan isnt working. The second cooling fan for. The ac condenser comes on with ac activation. Check the fan, the relay and the ect sensor. A pressure test should reveal any leaks. It could be just running out the overflow.