Well, I've got a coolant pressure leak. It seems to be from near the rad. cap, but I replaced that twice already, and I still can hear it hissing. I can only find it if the car (87 TPI 305) is driven hard and is REALLY hot (never gets above 240), then when I park it's boiling in the overflow and I can hear the leak. What's up with that? Any ideas of where/what I should replace?

 

Have you checked the overflow hose for leaks?

 

I didn't see any on a cursory inspection, but I'll do a more detailed check.