Replacing Coolant Temp Sensor, M103 300E
 

Hi,

Looks like I may need to replace the 3-pole temp sensor on top of the block, it doesn't trip the aux fan at 105+ degrees, but the fan circuit seems okay since I can get it running by jumpering the plug at the sensor.

My question is how do you replace the sensor? It looks like it fits a large (19mm?) wrench, but I have no idea how to get a wrench in there, since the valve cover blocks one half, and the wiring harness + fuel line block the other half. And I can't get a socket on it, because the head of the sensor is bigger than the "bolt" portion of the sensor. I know it can't be that difficult, since others have done it, but I don't see the way.

Oh, and I'm assuming the sensor location is open to the coolant supply, right?

Thanks,
Anthony

Yes, that sensor goes directly into coolant.


IF you replace the sensor with the engine COLD you can do that with-out losing coolant. start by removing the radiator cap, squeeze the upper hose, & re-install the cap with the upper hose still collapsed(still squeezing it).
That will create a vacuum allowing you to replace that sensor.

OF course draining & refilling with fresh anti-freeze is also a good thing to do with winter coming on...every 2-3 years for fresh anti-freeze is still a good idea.

Thanks for the tip on the coolant, that'll be helpful when I have to open it up. Anyone have any other thoughts on getting to the sensor itself?

Thin wall Snap-On socket....or buy a cheap one and grind it down.

.