During the past month, the engine temp on my '95 E320 Wagon rises to 115 C after idling for > 5 minutes. If the engine is revved a couple of times, the temp will almost instantaneously drop to < 100 C, but then will gradually climb again while idling. Temperature is okay while driving; around 95 C.

Auxillary fans work fine: low comes on with A/C (which is almost all the time in FL). High speed at approximately 98 C. (This is a bit lower than standard which I changed some years ago with a || resistor, based on input from here). Engine fan clutch seems to be coupled during these high temp situations. Car has 140k miles. Original radiator. Water pump, thermostat, and coolant cap replaced in April of 2002, 98K miles with factory parts. Coolant is flushed annually. The radiator seems evenly hot.

I'm thinking this is a coolant flow issue due to the fact that temps drop to normal when the engine runs above idle: perhaps a weak water pump or clogged radiator. Any thoughts or experience with this situation? Thanks.

__________________
as ever
Paul

1989 560SL
1987 300SDL
1987 300TD
1983 BMW 633CSi
1972 280SE 4.5