I need to diaognose an overheat problem w/ my 1992 300D
111K..

If I run the a/c and end up idleing in traffic the temp works its way up to over 100c-110C
If I acellerate hard the temp rises also.

Most of the components are expensive and I don't want to go on a wild and expensive goose chase.

I have cultivated a relationship with a mechanic at Park Place Mercedes & I think he is knowledgeable. Should I pay the diognostic fee or work it out myself.

I am confused about when the aux fans should come on and how to test the fan clutch.

ANY ideas passed my way will be appreciated!

Wayne

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Wayne Jockers
1992 300D

first do like this..

when it is "overheating" just feel on the radiator if the WHOLE radiator is warm, without AC switched on, feel on the lower waterhose from the radiator if it is HOT, than problably if the radiator is PARTLY hot and the lower hose is HOT u have a faulty Radiator... but if the engine OVERHEATING and lower and upper hose is COLD u problably should change T--stat, if the whole radiator is hot and the lower hose also is hot u problably need an new fan coupling =)


hope this helped u a little, and that u understood me =)

To be good for another 100k miles just replace the water pump, fan clutch, thermostat and radiator. Make sure you give it a good flush when you do it. All this work is diy'er type but I will say the water pump can be a pain in the butt.

Bad fan clutch will cause it to rise while idling. Radiator or thermostat issues makes it hot all the time. Change the thermostat first and see what happens. Next step would be the radiator. Does the coolant get changed every couple/few years? Personally, I consider a new radiator at 100k to just be good maintenance. Has it run any in the red? If it has there may be something up with the aluminum head.

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Jim