i've had a similar problem develop, but i havn't had the radiator get that bad on me yet. it started when it was cold as $hit and my car sat for 2 days. i started it up and there was a leak from the top of the rad. where the teeth hold the top in like you said. as time went on it was worse as i sat at idle than when i was running. it also seemed that the therm. stopped working b/c my coolant fan wouldn't turn on, but there was no issue with overheating at all. i just tried to keep coolant in the overflow which kept coming out, but now since it has warmed up the problem has seemed to go away. :thinking: no idea what happened, but sounds similar. hope i don't develope problems like yours. keep me posted on the solution to your situation...