Hello Scotty. I've got a conundrum. 2005 Pt Cruiser (non turbo), previously blown head gasket, replaced the motor with a lower mileage one. Pretty quickly afterward it started get air in the cooling system. Both me and a mechanic friend of mine have done Multiple head gasket leak tests that have all come up negative. I've gone through a whole bottle of test fluid. What it does is push air into the system and coolant into the reservoir which doesn't return. I use a turkey baster to suck it out and reenter it into the system. I would do that about once every tank of gas. Then winter came and with the colder weather, the problem at but went away. I might do this about once a month. Now suddenly, it is back and noticeably worse. It only takes about 50 to 100 mile to noticeably fill that bottle to where some coolant splashes out. There is NO overheating as long as I keep up with it and the car runs fine. I changed the overflow bottle line yesterday to no avail. Does this sound like a head gasket leak to you? I'm tired of testing for one but it's driving me batty. Please help. You're the best.