I hate to start new thread on this but I have searched and read other threads and I think mine is a little different. Rebuilt V6 engine. Replaced pretty much everything including both plastic cooling system hoses, water pump, thermostat, radiator, degas and cap with genuine motorcraft, ... Some probably know from other thread that I was fighting a P0401 and then P0402. Fixed both (swapped DPFE hoses (ouch stop beating me ) and vacuum leak. Ran like a top for 40 or so hard driving miles. Got back home and: Temp guage went a tiny bit above half way (had been right at halfway point every time I previously drove it after rebuild). Parked it and opened hood and the degas bottle was full, full, full. It had the right amount of coolant and I did bleed it weeks ago. After a short time, there was coolant on the ground. Looked to be in the typical place the degas leaks. So I'm thinking air (or some other gas - ugh) is in the system. But how is it getting in there with all new cooling system parts? I did not check for heat and the AC remains uncharged. Any ideas? Thanks.