Preglow Engine Coolant Temperature Sensor - PeachParts Mercedes-Benz Forum

shoe · #1 09-18-2003, 10:10 PM

On my 96 E300D anyone know where the preglow engine coolant temp sensor is located? I have a component locator and it appears to be near the thermostat housing. I cant find it there, any help would be appreciated.

shoe · #2 09-19-2003, 05:22 PM

Somebody has to have a clue!!!

psfred · #3 09-19-2003, 07:40 PM

Keith:

Temp sensor for the glow plugs is probably in the glow plug relay on the driver's side fender, not on the engine. At least it is on the 603 engine. Senses ambient temp only, so the GPs will run even with a hot engine.

Peter

shoe · #4 09-20-2003, 07:38 PM

Peter,

I agree there is probably one in the controller. However, the component locator I am referencing is from Star Tek Info. http://www.startekinfo.com/StarTek/ (Mercedes sponsored) clearly shows two engine coolant sensors, one for the gauge and one for the GP's. The one for the gp's apears to be a three wire affair. I keep getting a check engine light and a code of P0308 which indicates a problem with the glow plug system. Since the car has no problem starting I am suspecting teh coolant sensor may be giving a bad signal intermittantly. I want fo find the sensor referenced in the literature I have and take voltage readings and compare them with what the factory asys they are supposed to be.

mr. Goodwrench · #5 09-20-2003, 08:54 PM

The glow plugs failed to come on on my '93 300SD at 50,000 mi. It was due to a faulty temp sensor. It is located on the cylinder head just behind the second glow plug. mine is light green in color. It was not easy to change. Yours will probably be more accessable being that you don't have a turbocharger.

shoe · #6 09-21-2003, 11:07 AM

Thanks, I will have to pull the intake off but that is not a big deal. Do you think a faulty temp sensor would make the GP's come on after the car up to running temp? it has done that a couple of time right before the CEL has come on, actualy the CEL came on when the GP light comes on after the car has reached normal operating temp. It will stay on for a couple of minutes. Then I have to reset the CEL.

mr. Goodwrench · #7 09-21-2003, 01:54 PM

Your dashboard indicators are obviously different from my '93 300SD. If there is a malfunction of the glow plug system on my car the glow plug light comes on for a few seconds just after the engine starts, never after it warms up. The check engine light has never come on for any reason in the 8 years that I have owned this car

You may have a problem beyond the sensor. I would be suspicious of the engine wiring harness. You could be given a false warning indication due to wires that are shorting out or grounding intermittently. Since your car seem to start normally I would suspect that the sensor is OK. My car has 66,000 mi. on it and I have noticed cracked insulation both longitudinal and radially. However it has not ben a problem. Mercedes has made a repair harness available just for the engine compartment for most '92 to about '96 models which had the troublesome wiring.

shoe · #8 09-21-2003, 04:50 PM

Yes, mycar is OBDII compliant therefore the glow plugs are covered in the emmisions circuitry. I will give the wiring a look the next time I am under the hood.