Temperature Gauge Now Only Reads 50/60

[toolman1954]

Hi, vehicle is 1997 300TD , I recently did a 400 mile journey up to Scotland and almost there I noticed the temperature gauge falling from its normal centre 80 degrees position down to about 50/60 degrees. Because I was so far from home I just monitored the situation and did nothing as there was no immediate problem.
I just did the same 400 mile journey home, the engine ran faultless purring away at about 2500 RPM. @ 75 mph and the gauge is still reading low. There seems to be nothing else wrong with the car.
So is this an engine temperature sender fault?? and if so where can I find the engine temperature sender, I have looked and cannot see one. Failing that, is this some other electrical fault causing a low reading.
Comments appreciated -- Thanks.

 

[DSM10000]

It will be the thermostat that is faulty and needs replacing.

 

[Benzowner]

Agree^ the thermostat is probably stuck open. Other symptoms maybe taking a little longer to warm up

 

[toolman1954]

Hi, Thanks for the diagnosis, now having done a search, it seems that this is a common problem throughout the range of engines. I will get a thermostat and fit it .

 

[aspguitars]

Just as a point of interest, my 2001 C220 CDI was running at no more than 40 to 45. I bought a kit from Mercedes which consists of the thermostat housing with thermostat, the sensor and the rubber seal. £43 all in. I changed it yesterday and it now runs at about 80 degrees. Nice and warm now!