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1990 300SE
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4 Posts
Discussion Starter · #1 ·
Hello everybody,

My 300se, 130K, has been running hot for the last few weeks. Its been fairly cool so far in central Florida and the temp is running 100 plus.......during slow traffic, stop and go it runs right up against the red line 120 or so (Both fans run, no radiator leaks). I changed the plugs, wires, dist cap, rotor and she is still doing the same. I've read that maybe the ignition coil could be the cause but, I wanted to see what you guys thought. I'm using the official Benz coolant 40coolant/60dist water, level is good and that's all I know. Could it be a thermostat problem?

Any guidance would be appreciated. Thank you in advance for your help!

Johnny
Dade City, Fl
 

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2000 e320 4matic
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3,401 Posts
Welcome to the forum. Search "thermostat" in the forum using the upper right search function. There's lots of detail on the symptoms of a bad thermo. You could also search the 124 forum as the M103 engine finds a home in those cars as well.
 

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2005 W220 S500 4Matic / 2008 W211 E350 4Matic
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997 Posts
Thermostat or radiator are likely culprits. Do a search for thermosat here, and make sure you read about "Drilling the hole." Trust me. Also, don't let your car get past 110!!! You can fry much more expensive parts than a thermostat that way - like basically everything inside your engine! Running at 120 puts you in serious danger of a head gasket failure or worse, so do be careful.
 

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Depends on the day!
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13,337 Posts
FYI, even though M103's typically run warm well beyond the realm of normal. I'd pull your t-stat to start (I'd rather see her run too cool for a while then @ those temps all the time)and pick up a new one.

Flushing the system would be Wise, but Please use the correct Mercedes/Zerex G05 coolant...I'd run a 30/70 mix given where you live.

Has the water pump ever been replaced? Fan clutch? Are your Aux fans working?

Jonathan
 

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1991 300SE
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1,435 Posts
Had the same problem once. Turned out to be the thermostat AND my low speed fan resistor. Happen during the summer, so my AC was on and the T-stat was closed. So hardly any water was circulating or cooling. Only relief I got was when the hi speed fans reach temp on the sensor and kicked them on to cool the engine a bit. Very scary. :(
 
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