Wow. You were right. The darn cap. Ran the car all day and with the cap only on half way and some, Not too tight and it let out the needed pressure. No boiling over or anything. I guess just enough to let the system work normal. Lesson learned. Buy oem parts. Thanks a bunch. I can't believe it. Hats off pal. And thanks. Tom

I am going to install the oem Radiator,Cap and all the sensors and hoses to be safe. Wow and it was only the radiator and cap problem. Well once again I thank you all for the info. Ready Rad is not a good fit for this car. Buy OEM Parts. Cost me as much in the long run anyway. Don't go cheap with these cars. Thanks.

Well, I wouldn't have predicted that if someone just asked me about using aftermarket radiators in general.

Look in the radiator cap, there's actually THREE functions that the cap has to do. Each one is a smaller & smaller spring-loaded disk under the cap.

Largest ring seals against the upper lip of the radiator neck. That's the overall seal so it doesn't leak OUT.

Next smaller ring/disk is spring-loaded against a "ledge" inside the radiator neck. That middle-size disk will lift at a certain pressure (1.1 bar = 16 psi). That lets antifreeze out through the little hose to the white plastic reservoir. That's the one that controls the overall pressure in the system.

The smallest disk has a pretty light spring, in the other direction. It opens up to allow the radiator to suck the antifreeze back in as the engine cools down.

I always felt that understanding WHY stuff is designed that way; helps me to figure out why it doesn't work.

Well...The factory radiator and oem cap and coolant sensor installed. No Leaks. All this over a bad design of the (2) aftermarket radiators. Too thick where the cap twisted on. (The tabs). Thanks again for all the Help!

Thank you for sticking with it and coming back with the "answer"...:)