Its normal for them to warm up a bit at idle, no more than 212F(100C) though.

How old is the thermosat. I just put a thermostat in a 73 450SL and the old original unit came out in pieces, it corroded so badly it was stuck to the block.

Touch the 2 wires that go to the aux fan switch on the AC drier together, the fan should turn on. If it does then you need to replace the switch on the AC drier, and the 212F switch on the motor is self.

It also never hurts to replace the sensor for the gauge on the dash, over time they being to give out false readings.

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1985 300TD Turbo Euro-wagon
1979 280CE 225,200 miles
1985 300D Turbo 264,000 miles
1976 240D 190,000 miles
1979 300TD 220,000

GONE but not forgotten
1976 300D 195,300 miles
1983 300D Turbo 175,000 miles

http://i42.photobucket.com/albums/e3...e485-1-2-1.jpg