I have a 1987 300E. Ever since I purchased the car it has it has an erradic over-heating problem.

When in slow traffic or at idle the car temp rises above 90. I can hear the auxilary fan cut in at above 90, but it seems too late and car has doesn't cool down unless I start moving again. I've never let it get to 120 as I usually am able to get up to speed forcing air over the radiator and cooling things down.

I had the car serviced last week. They replaced the thermostat with a 80 instead of an 87... seemed too low for me. When I left, the car got hot again immediately. Upon inspection, I found out the fuse was blown on the Aux fan....(stupic mechanic).

I had it served again this week by someone else. He replaced the thermostat again with an 87 degree one. He let the car idle for 2 hours with A/C on.. no overheating. Next morning in the commute to work, it began to overheat upto 110 degrees. Fuse is not blown, aux fan is coming on, but I just don't get why its happening.

Bad aux fan switch, bad fun clutch, bad temp gauge, possession?

Thanks in advance for any help.

Eli

The fan clutch on these do fail and will cause this!! The temp gauge can be checked for accuracy with a resistance substitution box...I don't remember the exact ohms. Your QUALIFIED technician will be able to help.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

I have a 1986 190e 2.3-16 valve that suffered overheating as well. After the radiatior was replaced due to it blowing a leak, it overheated again but I caught it before anything happened. I suspected the fan switch that controls the fan clutch. My car has two fan systems. One is the fan clutch itself. The second is the auxiliary fan the comes on when the a/c is used. My car now hovers around 87-100' C. That is normal operating temp. A darn cheap switch controls the fan clutch. It cannot be checked so I just replaced it. Try it.
Joe

The fans on the 190 are BOTH electric that is why the fan switch is so important!! The 300E uses one electric (aux fan). The engine main coolant fan is connected direcly to the engine via the fan coupler. And if the fan coupler is working properly, the fan works all the time.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM