I have it isolated to the cap being the problem, but both my original cap and the new cap actually hold pressurewhen it cools down. Hell, this morning I was hoping to see less coolant in the recovery tank. After 12 hours of sitting over night, the stupid radiator still had pressure. I hope this is an obvious problem. If I knew exactly how the radiator cap funtions, then I could continue troubleshooting. I called the people that distribute the radiators, but they just sell radiators, not the caps.

So my question is: what do you guys think is keeping the pressure inside the radiator? Maybe the plunger being too compressed or not compressed enough?

can a radiator cap be on too tight?
What are the odds of busting a coolant return hose?

Please help me.

 

Sounds like a good time for a radiator upgrade. Just get a new Del Sol Vtec Dual Core Radiator.