I believe that I have found the problem with my cooling system, it is not definite but I want to take a gander at this annoying problem. So, I want some insight on replacing the Engine Coolant Temp Sender or whatever that part is called which lets you know the coolant temp in a Mercedes Benz 300 D Turbo Diesel. I want to know the difficulty of putting a new one is, what tools to use etc. The reason I believe this is the problem and is faulty is it seems to jump around like it has a mind of its own. noticed my temp guage went up around two millimeters below the white line under 120 degrees celsius after the car had ran somewhat cool I guess, and then after religiously looking at the guage it flickers up to that mark. I then pulled by the video store and shut the car off with the guage remaining at that mark and after shutting it off and turning it back on it was giving a reading of around 100 or less I dont quite remember the exact temp. After that I drove it back home and it was around the mark that it was first at so haha. It seems like the faulty componet. So guys help me out on how to replace this part.

The part is located at the right side of the engine block (if your standing directly in front of the car, where the glow plugs are located its a brass colored and its connected by a plug, if i can remember you need a 17 inch wrench to take it out, and remove the plug, just be sure that you have a washer on that thermo senser or else it will leak and try not to kink the injector line....

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Current Garage
2008 Mercedes GL320 CDI 188k mi Repair/Work in progress
1994 S350 160k mi Garage Queen & prepping for repairs
2005 E320 CDI 203k mi Healthy & Daily Driver
1994 S350 357k mi Retried as parts car
1984 300TD 214k mi Blown OM617 Poss OM603 Swap??

Sold
1987 300SDL 200K+
1994 S320 181K mi
2008 E320 Bluetec 127k mi
1999 S420 130K mi
1980 240D 360k mi
15+ Others that has come, stay and gone

GONE, BUT NOT FORGOTTEN
1995 E320 SE 220k mi
1984 300SD 350k mi

If the needel on the Temp Gauge is jumping around I would not rule out a loose electrical connection.
The temp sensor is on the side of the Cylinder Head behind the IP.

I also had a Coolant Temp Sensor that was not working right and when I pulled it I found it was covered with deposits. After it was cleaned off and re-installed it worked.

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84 300D, 82 Volvo 244Gl Diesel

I have the same problem and can not locate the temp sender on a 1987 300SDL. Is it located somewhere on thermostat housing(?) behind the alternator ?

Thanks ...

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1987 300SDL 314K mi, counting; #22 Head
1999 E300Turbo 405K original miles
1997 E320 180K mi (Son's)
2002 ML320 (Son's)
1998 S320 140K mi (Son's) sold
1985 300SD 311K mi
1984 300D 324K mi (killed by a hit-n-run turd)
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You might look through here:
http://www.ps2cho.net/downloads/MB%20CD/W124/Main.html

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84 300D, 82 Volvo 244Gl Diesel