Engine not warming up

[xf8u39]

Guys, I have an issue with my '55 CLK270 diesel.

When I start the engine the radiator cooling fan is running constantly. The engine barely gets warm during driving.

I have ordered a new thermostat, coolant temperature snsor and coolant level sensor.

Does anyone know why the fan runs constantly? I have given it a good eyeballing, and cannot see any wires going to the fan, so I can disconnect it temporarily.

Rgds

Michael.

 

[Oleks1992]

Guys, I have an issue with my '55 CLK270 diesel.

When I start the engine the radiator cooling fan is running constantly. The engine barely gets warm during driving.

I have ordered a new thermostat, coolant temperature snsor and coolant level sensor.

Does anyone know why the fan runs constantly? I have given it a good eyeballing, and cannot see any wires going to the fan, so I can disconnect it temporarily.

Rgds

Michael.

You need to check for fault codes, could be a lin bus fault with fan module

 

[Uky]

MB does sometimes manage to hide cable harnesses well...

A not to uncommon problem is water ingress into the connectors of different cable harnesses.
Or that one or more metal sleeves becomes dislocated and fails to make proper contact
with either a sensor or the CAN/LIN/K-Line parts of the system.

If the fan controller connection to the engine management systems is lost,
the fan will run constantly in order to protect the engine.

Another cause could be that a temperature sensor for the AC is open
or short, indicating a system overtemperature which would also start the
engine fan. (Is the AC "ON" or "OFF" ?)

My own experience with this is a C207 where several sensors for the AC
was placed at the left side bottom of the AC radiator. A place exposed
for salty winter roads and also inaccessible unless using a car lift
and removing some of the plastic protection sheets.

My advice is to take a second look and see if you can find the connection(s)
and proceed from there.

It is too simple for an inexperienced mechanic to only check for error
codes like "No communication between X and Y" and then simply replacing
the module (££££), never realizing that it was a loose connector that was the problem...

 

[xf8u39]

Thanks for info. The only message I am getting on the dash is check coolant level. I have done this and all is well.
I think after I have replaced the stat and level sensor I will break and make as many connectors as I can find and take it from there.

 

[xf8u39]

Oh yes, I forgot to mention. I have turned the AC on and off. Fan still running.

 

[Uky]

Regarding the engine coolant: Some brands uses a sensor that simply
measure the resistance between two metal strips to check the level.

A small current flowing = level is above lower limit.

Cars that uses resistance measuring for coolant level check does allow the use
of ordinary tap water since de-ionized water will not conduct any electrical current.

If your car has a mechanical level indicator, the coolant level is OK and the dash
still displays "Check level" I would suspect either an open circuit or short somewhere...

Note that sensor circuitrys are checked for open, short or returned value out of possible range.
Any of which will result in a warning message.