CLC 220 (CL203) Engine Running Temperture

[tgl3]

Hi guys,
Recently I have noticed that the running temperature of engine seems not right... I live in the midland and in UK winter weather the engine temperature guage indicates the engine constantly run at approximately 70 degrees after drive for about 100 miles (1.5 hours) on single carriageways (A roads). I read lots of other threads where most people say their engine constantly runs about 90 degrees, which is definitely different to my case. I was wondering if there's anything wrong with my engine or if I should replaced the thermostat as most people recommend?
also, I would like to ask owners here of the same model as mine;what about the fuel economy of your car? as I belive mine did much worse than other same model car. I usually pumped with BP fuel and in the city I got around 30 mpg and the best is on motorways where I could got about 45 mpg; one full tank diesel returns me about 400 miles if it used to commute only within the city and no running on motorways. Is that normal...?

 

[tgl3]

I also reckon if the cold temperture contributes to the low running temperature...?

 

[tgl3]

What I also think should be added here: after intermittently overtook 2 cars on the single carriageway in 10mins, the indicator of the gauge hardly went up to almost 80 degrees and few minutes later it dropped down to the range between 60 and 70 again.

 

[MrGreedy]

Cold should not significantly contribute, as when cold, the thermostat should be fully closed, except for a trickle hole. In that even, the engine coolant is not circulating through the radiator system, so it should get up to operating temp pretty quick (whatever that is). Most modern cars run somewhere near 90 degrees. 70 seems very cool.
Either the sensor isn't working properly, or the thermostat.

Most temp indicators normally indicate a range of temps when somewhere towards warm. E.g. old school dials typically move the needle between 70 and 110, with below 70 resting on the needle, and above 110 meaning very hot. On my w203, it was viewed via dash settings, and as well as the number, it showed a horizontal bar. When the temp was at 90 degrees, the 'progress' or width of the bar was about 50 percent of the way across the screen.

Do you have any indicators like this?
I'm sure someone will be along to advise of the exact correct running temp.

 

[tgl3]

Cold should not significantly contribute, as when cold, the thermostat should be fully closed, except for a trickle hole. In that even, the engine coolant is not circulating through the radiator system, so it should get up to operating temp pretty quick (whatever that is). Most modern cars run somewhere near 90 degrees. 70 seems very cool.
Either the sensor isn't working properly, or the thermostat.

Most temp indicators normally indicate a range of temps when somewhere towards warm. E.g. old school dials typically move the needle between 70 and 110, with below 70 resting on the needle, and above 110 meaning very hot. On my w203, it was viewed via dash settings, and as well as the number, it showed a horizontal bar. When the temp was at 90 degrees, the 'progress' or width of the bar was about 50 percent of the way across the screen.

Do you have any indicators like this?
I'm sure someone will be along to advise of the exact correct running temp.

Thanks mate for helping here-
The image shows exactly what my dash looks like and the needle rarely goes to the middle between the lowest and the highest as it usually swings within the range I marked with red lines in the image, mostly stick to the lower part of that range.

 

[MrGreedy]

Great stuff. So based on my rubbish rule of thumb, I'd always expect any modern car to be rock solid in the middle of the dial, so 80 degrees in this case (severe summer thrashing aside). The temperature reported here is one of the temperature sensors on the car, and is usually a water/coolant temp rather than engine oil, and is often not the temperature sensors used for ECU calcs/engine running.

Something is wrong with your temps if it's always hovering around the bottom end.

You could use your VIN in the Mercedes zap online catalogue. If you put your VIN in, you might be able to have a root round the pictures, and find out the part numbers (and hence price via google) for a new coolant temp sensor and new thermostat. This will help you decide which route to take e.g. if the thermostat is a million quid, then a diagnostic at an Independent Merc specialist would be a good first spend of £50 to avoid part swap roulette. If the parts are £20 each, you might fancy changing/getting them both changed.

 

[MrGreedy]

One other thing,; if it isn't stable after, say 15 minutes, and varies up and down by more than barely noticeable movements, it could also indicate air trapped in the coolant system.

 

[tgl3]

One other thing,; if it isn't stable after, say 15 minutes, and varies up and down by more than barely noticeable movements, it could also indicate air trapped in the coolant system.

Thanks mate for advice again
It will not noticeably move up and down as it always stay at the same temperature (about 65C) after the car warm up. The only thing will trigger the needle move up is if I fully push the pedal (WOT) for a while for things such as overtaking; after that, around 15 mins later, the needle drop down to 65 again...
I’m now checking available parts online that you suggest me to replace. They are not that expensive, but not really cheap either; including labour I assume at least 100 quids are required

 

[Stratman]

It should run at around ninety degrees come rain or shine. I'd say with 99.9% certainty it's a faulty thermostat, a common problem on Mercedes throughout the range. An easy DIY job, but I'd advise using a genuine part. Some pattern copies are even less reliable than OEM.

If you do the job yourself, be careful of the plastic fuel pipes that run next to the thermostat. They get brittle with age, and can crack if handled with anything less than gentle care. Getting the running temperature up to where it should be will certainly improve the fuel consumption too.

 

[amazighman]

Agree with the above post.
Faulty thermostat is your problems.
Easy job to change and a good quality OEM like Mahle are only 20 quid or so.
20 min to change

 

[tgl3]

Thanks guys for contributions
I’ve just reached some of my local garages; I had been told by three garages that the average basic labour cost for doing that is about 120 quids (highest hit 170 quids), which’s even more expensive than the part itself. Is it really need that much time (about 2 hours)...?
What a nightmare

 

[amazighman]

Easy job if you can do it.
120 pounds is too much to pay.
The part is circa 20 quid? 100 pounds labour for a 10min job?

 

[rf065]

Some Mercedes dealers discount their labour rates up to 50% if your car is a certain age, worth asking any near you. The prices you've quoted don't sound any better than the main dealer prices for a min 1 hours labour. No way should it take longer than 30 minutes.

 

[tgl3]

Easy job if you can do it.
120 pounds is too much to pay.
The part is circa 20 quid? 100 pounds labour for a 10min job?

That’s what really confused me, I don’t know why they charge so high for things can be done within 20 mins as many people said?
Well, as I don’t have any tool or skill for doing those mechanical stuffs I usually reach garages to solve issues, and I’m also kind of people easily to break other things when trying to do these mechanical skilful works by myself But I can probably try that if anyone can provide me some instructions or manual

 

[tgl3]

Some Mercedes dealers discount their labour rates up to 50% if your car is a certain age, worth asking any near you. The prices you've quoted don't sound any better than the main dealer prices for a min 1 hours labour. No way should it take longer than 30 minutes.

I’ve reached 3 garages and none of them quoted a prices lower than £120
I don’t know why that happened but I think my car is not that old (2008 model) need to charge a such high price for works can be done within 30 mins.

 

[rf065]

but I think my car is not that old (2008 model)

It's old enough to get a discount from any Mercedes dealers that have that option. The one I used to use, gave 50% off labour & 10% off parts after the car was only 7 years old.

 

[amazighman]

See if someone from the forum will do it for you.
Where are you based?
I assume your engine is om646 so it is indeed a straight forward job

 

[tgl3]

See if someone from the forum will do it for you.
Where are you based?
I assume your engine is om646 so it is indeed a straight forward job

I live in Coventry now; will be really good if anyone can help there

 

[tgl3]

I just reached one garage who told me they can do that for £70; before they quoted me a price they asked me if I want to do the front thermostat or the rear one, I was confused because I though the front one is the only one so I did some research and I realised there’s a exhaust thermostat as well. I’m wondering if the high labour costs mentioned above are all towards the rear thermostat replacement because I didn’t mention which one I intent to replace during conversations so they probably though I would like to replace the rear one and quoted me that high prices...?

 

[amazighman]

70 quid is ok.
Your issue is the coolant thermostat.