89 300sel question

[wrnmnro]

what is the little 2 prong sensor on the head of a 103 engine? Has 2 lines running from it and is threaded into head for obvious temp sensing. would this affect idling? What is it called so I can order one..I broke the tips on mine!

Thanks
Warren

[pawoSD]

Yes that is a temperature sensor. If it is just two prong it might just be the one for the gauge in the dash....does the gauge still work? If not, that is it. If it is still working, then the sensor is for the ignition computer. It should be obvious if you search the parts site for a temperature sensor which one it is, based on the pictures.

[outofspec]

Hi Warren,

It sounds like you’re talking about the sensor with the two vacuum lines running to it. It’s nearer the front top of the head. I’m not sure what the name is but I believe that what it does is allow gas tank fumes from the charcoal canister to be sucked into the intake once the engine reaches operating temperature. You’ll find a line that runs from the canister outlet on the left fender of the engine compartment. It goes down to what I call the throttle plate. I think its more EPA related then engine management, but if yours is broken there’s a vacuum leak.

Outofspec

[pawoSD]

I'm pretty sure a 1989 300SEL does not have a charcoal canister....my 1990 300E does not....

[outofspec]

I had 2 1989 300SEL's and currently own 1 1990 300SEL and they all have vacume line outlets on the left fender well for the gas tank vent through the charcoal canister. The canister is placed on the inner fender well out of sight. I'm not sure that's what Warren is asking about. The only reason I thought that is because he said "Lines" not "Wires". As information the sensor for the temperature gauge only has one wire going to it.

[pawoSD]

Earlier CIS injection temp sensors have two pins:



Later ones switched to a 4-pin connector (in 1990)

[rocky raccoon]

That is definitely the engine temp sensor for the CIS. Non-function will affect idle and hot driveability. Cost about $45.00 from FASTLANE Phil.

[Arthur Dalton]

All gauge sensor/thermistors are single pin, wired to ground.

[pawoSD]

Originally Posted by Arthur Dalton

All gauge sensor/thermistors are single pin, wired to ground.

Very true....wasn't thinking straight.

[Arthur Dalton]

Yeah...here is a little more info fo the gauge sender , in the event one wants to check either the gauge OR that sender.

Get a 38 OHM resistor and solder an alligator clip on one end and a bullet connector on the other.

Now, if you ever have a gauge or sender reading problem to diagnose, just unplug the sender connector and plug in your new tool , clip to ground, turn on the key and look at the gauge.
It should read exactly 100C.
If yes gauge is fine..and sender is the problem

This simple substitution eliminates the wireing, etc for possible problems, and also checks Ahe accracy of the gauge with the same test. Benz gauges are usually right On [ in comparison to Asian ,hwere they take a Mean reading]

[wrnmnro]

Thanks to all, I found the part on line for 50.00...since only the prongs were broken off I made my own prongs and put them on the unit and installed....seems to work...but I am having idol surges

[Arthur Dalton]

Sowhich one was it????????????????????????????????

[wrnmnro]

the 2 prong ...called a thermo vacuum valve....color coordinated for your specific car...Gauge inside worked fine before so it must be egr related

[Arthur Dalton]

Originally Posted by wrnmnro

the 2 prong ...called a thermo vacuum valve....color coordinated for your specific car...Gauge inside worked fine before so it must be egr related

Very Good..OutoSpec was correct.

[outofspec]

Thanks for the recognition Arthur.
Even a blind squirrel finds a nut once in a while.