Title says it all. I’ve been battling overheating issues with my cobra since I’ve owned it and I’m at a loss at this point. Basically after I replaced water pump(preventative maintance), new sve radiator(old one shit out), thermostat, and cap the car ran fine for two weeks or so. No overheating etc. the car then lost heat ( no overheating, just not heat) so I just went about by my business for another few weeks and while sitting at a light I saw the temp crack a bit over halfway as if it was going to start overheating. Finished my drive to work with no issue. After work drove the car for 15 min at operating temp until the car started to push coolant out of the cap and overheat. Let the car cool down and filled it up with water and basically did this a few times. Drove as far as I could until the car started to get hot and shut it off and repeated. On about the 3rd or 4th go the car didn’t overheat and I was able to finish the last 10-15 miles of my drive at operating temp. I did notice the temps creep up once I made it home. The car does not get hot at idle but only after I drive it for 5 minutes or so it pushes coolant out of the cap. I have tried completely bypassing the heater core. Fan is working, I’ve pulled the radiator out and it’s clean with nothIng affecting flow through there. The upper hose on the radiator is definitely a touch warmer than the lower. The thermostat really only fits one way so I don’t believe it’s backwards. Oil on the dipstick looks fine. Could the expansion tank just be bad and causing my issue. Another thing I notice is after I fill the resivour over about a night it’s near empty if not empty. But the hose running into it from below always has coolant in it up to the resivour almost. I know the oil cooler leaks and I have a rebuild kit for that. The issue seems like a headgasket problem but the car doesn’t smoke any, runs fine, and I can’t see oil mixing with coolant on the dipstick. Could a stretched belt be causing the water pump to be “slipping” per say and not push enough coolant through the engine to cause an overheating issue while driving? I know a leak down test would be a sure fire way to tell if it is a headgasket but I need to be able to get my car to my work to do so, so until that happens that really isn’t much of an option.