Overheated on track - now what?

[infernosg]

Both valid points. What seems to be missing though is any sign of an external leak. I'm not seeing anything from any of the lines; nothing from the radiator and nothing coming out of the "weep hole" on the water pump housing. By "signs" I mean no leaking fluid, no evidence of dried fluid, no steam while running, no coolant smell, etc. Also, if there were a small leak allowing air into the system wouldn't that air just bleed off and stop at some point? The system is pressurized when the car is running so wouldn't that prevent additional air from entering?

I'm not sure if I'd say the pressure test "passed". I brought the system up to 15 psi and within 10-20 minutes it had dropped to 14 psi. You would think a perfect system would hold pressure indefinitely.

I still think I'm missing something about the bubbling in the overflow bottle. Something is causing a pressure build-up in excess of 0.9 bar but it's not a constant stream of fluid that's coming out like what would happen with an over-filled system. It's a mostly steady stream of gas, whether it be escaping air pockets (but they never stop), boiled fluid (possibly a result of a stuck thermostat) or exhaust gases I'm not sure. I suppose the only way to tell is to have the system checked for the presence of exhaust hydrocarbons but I don't know where I'd go for that.

I have a new thermostat that is not yet installed and a new radiator, water pump and full set of hoses on the way. Is there any hope that installing all those would rectify the issue? If not, I guess I'm just going to have to tear the engine apart.