Hello I have a 2008 Tahoe and when I turn on my ac the engine starts running hot and the sensors turn off the ac and messages start popping up like reducing engine power or engine hot so when I get out to check there is no coolant in the tank but the only external leak I can find is coming from the normal drip from the ac and there is no fluid coming out of the exhaust pipe and the oil looks brand new so any ideas why I'm losing coolant only when the ac gets turned but can't find a leak? . . . . . Any help will be appreciated