This has just become my #1 problem in the past week or so. Therm. ok. Cap seems ok. No extra pressure in the morning. I too am thinking radiator, but is there a way to test the pump as well? The "squeeze" test of the upper hose doesnt give me that much pressure, and I know the flow is low from trying to flush the system in the past. Do keep us updated!

__________________
Paul
2004 E500 4matic; 72,000mi