This is for a friend of mine... He's got a racecar, and on startup, after it has been sitting for a day, it will spit coolant from the expansion tank. It only spits while it is warming up, around 160-165*. Once it is up to temp, it stops. If you let it cool for a while & restart, it is fine. It only happens after it has been sitting for a day or more.
It has a 350 engine, double pass radiator, & expansion tank. Both the rad & expansion tank have 28lb caps, which have both been tested and are good. It has no T-Stat. Compression & leakdown tests have been done & all is good, so I know that compression is not entering the coolant system. The water pump has been checked as well, and is good.
Another oddity, is that if you let it sit for a day or more, with the engine cold, if you pop the rad or expansion tank caps, coolant comes out like it has @ least 5lbs (or more) of pressure. This is on a cold engine (not running).
Any ideas? I'm all out.