Oil loss, low temp guage

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Psabin8951

New Member
Joined
Dec 16, 2023
Messages
6
Location
Devon uk
Car
E350 CDI
Hi all, a newbie to all things mercedes and not a good journey so far. Many issues but latest on a 2011 E350 CDi is smoky oil smell diagnosed by indie specialist as oil cooler and main rear seal issues. Now all replaced.
I'm now finding temp guage either doesn't move at all or only goes to about 60.
When guage doesn't move ECO light and function is inoperative.
Any ideas? Temp sensor?
 
Welcome.

This could be due to a faulty thermostat, or air bubble trapped in the cooling system (the air won't conduct the heat to the sensor).
 
Can it be bled easily?
Just remove the filler cap, start the car and let it come up to temperature
You should see air bubbles in the top of the radiator if there is air still in the system.

The Eco light won't come on until the car is up to its correct operating temperature (85-90c on the new thermostats.)
If trying to bleed air from the cooling system doesn't raise the coolant temperature, suspect a new thermostat is needed.
 
Just remove the filler cap, start the car and let it come up to temperature
You should see air bubbles in the top of the radiator if there is air still in the system.

The Eco light won't come on until the car is up to its correct operating temperature (85-90c on the new thermostats.)
If trying to bleed air from the cooling system doesn't raise the coolant temperature, suspect a new thermostat is needed.
Ok so I'm thinking it must be the coolant sensor as when driving it went from 60 degrees to 0 instantly. Turning car off then on brought it back to 80 degrees!
 
Ok so I'm thinking it must be the coolant sensor as when driving it went from 60 degrees to 0 instantly. Turning car off then on brought it back to 80 degrees!
Quite likely. You didn't mention that in your initial post.
 
^ The coolant temperature sensor is a separate part to the coolant thermostat.

Part 85 in first diagram
Part 20 in second diagram.


 
I am not sure about the OM642 engine, but on a general note there are often two separate sensors, one is the coolant temp sensor that transmits data to the ECU, the other is a separate coolant temperature sender that sends data to the gauge on the dash. Worth checking.....
 
Just noticed mine an om642 is doing some weird stuff. Usually takes a while to get to 80, only way seems to work the engine a bit with higher revs. But today it was at about 70 and then dropped down to 0 for the rest of the journey. After a restart it started working again, although with the values it displays am not sure it is very accurate. Would an odb scanner reveal any live data to compare with?
 

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