Quote Originally Posted by hitman92499 View Post
Have you pressure tested the radiator cap or replaced it? Without pressure in the system, the coolant will be able to evaporate since pressure in the system increases the boiling point. Also, a faulty radiator cap will make it so the cooling system never pulls from the overflow reservoir. Just a thought.
Interesting! I didn't think of that. That will be the next thing I try. Do shops charge to pressure test?