W204 thermostat

[Mbstarz]

I have noticed on a 9 mile trip today, when I got home stat needle was at 60. I would have thought it would be at 90 as it was a good stop start drive. Outdoor temp about 6 degrees.

Would you suspect a problem?

How much would it cost to replace a thermostat using a genuine part?

Would a diagnostic pick up a faulty stat?

Note: I am getting about 24-27mpg around town which is poor

Cheers

 

[grober]

Diesels take a long long time to heat up [ its because they are more thermally efficient they give off less waste heat] Outside temp at 6 degrees is not hot and the car may have experienced some pretty low temperatures sitting overnight?? 24-27 round town is bit low but in cold weather perhaps not too bad. My gut feeling is that its probably not so far off the expected at this stage to warrant further work. If you have the later twin turbo OM651 engine they have a variable output engine coolant pump- I guess its possible this has developed a fault- assuming it "defaults" to a full flow condition? A fault code would possibly show this up.

 

[Bernie C]

Hi

I have a 320 Cdi and after 4 to 5 miles it is planted at 90 deg C - this is even at low ambients - I would definitely look at a thermostat replacement

Good luck

 

[ItalianTuneUp]

I had a similar situation. Car would struggle to reach 60C on short or even longer journeys of 50 miles. Also the heater was struggling to make the car warm inside.

Everyone I spoke to said: thermostat is stuck open.

Getting a new thermostat fitted including parts and labour was less than £100 iirc.

As soon as the new thermostat was fitted, the coolant temperature reached normal temps (80C-90C ish) reasonably quickly again, and the heater made it toasty warm inside pretty quickly.

 

[Chrishazle]

On my S204 C220, which lives on my driveway, within 4 miles of leaving home the temp gauge is off its bed and the heater is warming the inside of the car. Within 6 miles temp gauge shows 80+ and everything is toasty inside. In normal driving - mainly quite short runs - the dash shows 40+mpg.

Had a similar problem to yours with my S203 a few years back, new thermostat cured the problem - and increased the indicated mpg by about 5mpg!