OM617 Temp Sensor(s)

[techguy512]

I'm getting erratic temp readings on the gauge in my '82 300D. The problem is intermittant, but when fully warmed up the gauge will make instant transitions erratically between 85C and 100C.

I want to replace the temp gauge sender, so I bought one and I find there are two "sender looking things". One is in the head between GP 2 and 3, and the other is near the thermostat housing right next to the EGR valve. The unit in the head seems to control the gauge. What does the other one do? Coolant temp sensing for the climate control? Something else?

Art there any tricks to replacing the unit in the head? It came with an aluminum crush washer, but should I use anything on the brass threads before tightening it down?

Thanks,
Bob
'82 300D

[TheDon]

the 85 i own i just changed the one for the guage in the dash.. it is the second one.. not the first one.. easy way to make sure is take a paper clip.. make one end stick into the female plug and ground it.. if the temp guage spikes youve got the right one..

oh i misred your post

but the one for the guage is on the driver side of the block.. and on the 85 their are 2 sending units there. one for the gp relay and the other for the guage... read what i posted and you will find it

[Pete Burton]

The sender near the thermostat prevents the heater blower fan from coming on when the engine is cold. You can use antiseize compound on the threads. Make sure the head is clean around the threads because the sensor needs to ground to the head to send the correct temp signal.

[techguy512]

Thanks guys. Any guidance on tightening torque? I'm paying a lot of attention to this.