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Old 07-24-2011, 06:52 AM
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Join Date: Jul 2011
Posts: 90
M103 overheating at idle.

1990 300TE.
The TE runs at about 80 degrees c on the open road, but at idle in N, the engine temperature rises towards 100 degrees after 5 minutes and idling in D the engine pushes 110 degrees, but is very stinky with a scorched metal smell from the engine bay and exhaust.
There isn't any emulsion on the oil filler cap, the coolant is clean and the viscous fan turns, although the idle speed in D is just about 500rpm. The exhaust emissions at idle are 0.143% CO as set by the independent Merc garage. The car does not have a cat, a/c or electric fans as it is UK / Euro spec.
What temperature is the viscous fan supposed to cut in at? it is the bimetallic strip triggered version, not the magnetic triggered version.
Am I missing anything obvious?

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Old 07-24-2011, 07:28 AM
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Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 12,640
I don't think the fan clutch latches in till it gets above 100dC.

With the car at the 110d mark have someone inside turn it off while you watch the fan clutch. If it continues spinning for any lenght of time then it probably needs to be changed out or repaired. Do a search on fan clutch. There have been some folks that have successfully refilled it.
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Old 07-24-2011, 07:42 AM
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Join Date: Jan 2008
Location: Melbourne Australia
Posts: 834
Being a U.K. car and I am presuming there is no AC. Is there no electric fan in front of the radiator? Which operates from a temp sensor on the head.

Are you losing coolant?

Get a pressure check done.

You can have the viscous fan clutch refilled however I would be sourcing a Sachs OEM one. Next is a Behr.
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Old 07-24-2011, 02:41 PM
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Join Date: Aug 2002
Location: Southeastern PA
Posts: 3,037
How old is the thermostat? It's quite possible that the thermostat isn't opening fully when the engine idles.
Fred Hoelzle
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Old 07-25-2011, 12:16 PM
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Join Date: Jul 2011
Posts: 90
The fan spins on when the engine is shut off.

UK car, no a/c (everything was a cost option, even a radio), so no electric cooling fan.

I hadn't considered that. As far as I know the thermostat is original, although the radiator and water pump were dealer replaced five years ago.

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