W211 320CDI temperature (straight 6) & MPG

[MJH]

What engine temps should I be seeing on average ? Coming up our lane tonight after a clear 12 mile drive at 60'ish from work the gauge was about a qtr the way up, between 40 and 80. This seems a bit cool to me and I'm wondering if this is also why my fuel consumption has dropped lately ?

I was seeing an average 36-40 mpg a few weeks ago but at the moment I'm running at around 32mpg.

The temp is only something I've noticed today and I can't say I've ever really taken note of it before to know what it should be at.

The only other thing that's happened that may have had an effect is the battery's been off and the codes all reset when it went it to have a lighting fault looked. But, would this affect fuelling ? would the ECU's engine/transmission lose any settings previously adapted ?

Cheers, Mike

 

[whitenemesis]

Should be around 80-85c. Disconnecting the battery will have no effect on the ECU's. Possible thermostat failure

 

[renault12ts]

AS above, temp should be a steady 86. Stat is required.

 

[kwakdonut]

What was the air temperature? After 12 miles, mine is just getting to temp but it depends on the OAT. During the cold snap last week, 12 miles barely saw the car getting to 70c and no, my stat isn't faulty! It was changed a few months ago and is fine on a motorway run, showing a min of 80c.

If you do a longer run, does it get to 80-85 or not? If no, then most likely its the thermostat

 

[tagnut]

At only 50 degrees after about 15mins I'd say your stat has gone. Easy to check by doing a longer run of half an hour or so. As mentioned already operating temp should be above 80.

I've had the exact same issue for a while and just had the the stat replaced now gets up to temp no problem.

 

[s88]

Well I reckon mine is 80 and two digits which I think makes it 88, it has been like that for years.
it has also recorded 32mpg overall in my ownership, according to my excel spreedhseet which could be rubbish!
it will do over 40mpg on a run but in general it does short trips.

 

[pdd]

I've got a similar problem - car warms up qiuckly enough to 60-65 (usually dead on 60 or one bar above) but no more unless stationary for ages then drops back. Classic thermostat failure symptoms on any car.

Must be an epedemic because I called Eurocarparts and they didn't have one in the whole country.

Local Mercedes dealer quoted £40.40+VAT for the part including the gasket and sensor. Mercedes list it as a 92 degrees stat apparently so that's what the engine should be running at.

Once I get it fitted it'll be interesting to see what effect, if any, it has on fuel consumption.

 

[kwakdonut]

I've found it's best to get one from MB as it will fit and seal properly. It does include stat, housing and temp probe all in one so not bad VFM really.

 

[pdd]

I've found it's best to get one from MB as it will fit and seal properly. It does include stat, housing and temp probe all in one so not bad VFM really.

Yes, I do tend to agree. £40 for the stat, housing and sensor is actually quite competitive as thermostats go for cars.

The main reason I am slightly anti genuine Mercedes parts is that one usually needs to buy them because the rubbish quality original Mercedes part has just failed.....

 

[BlackC55]

MB parts are not poor quality at all. You should see some of the crap parts produced by aftermarket companies.

 

[pdd]

MB parts are not poor quality at all. You should see some of the crap parts produced by aftermarket companies.

Well, to be fair, MB's parts are made by the same companies as everybody else so are no worse or no better on the whole. They do seem to have a lot of problems with thermostats - above the norm I'd say.

Parts prices are always strange for all marques - sometimes the main dealer can be cheapest for certain parts. You just have to shop around - I've no problem with OEM parts at all although 3rd part non-OEM is another matter.

I have noticed a trend in recent years that a lot of parts are dropping in quality and in particular from manufacturers making cars in expensive countries (e.g. Germany). To protect margins they seem to be putting so much pressure on sub-suppliers the quality has suffered - it is the same story across most European manufacturers.

 

[pdd]

Well, finally got around to fitting it. Fairly easy DIY job.

Was getting to 60-65 and staying there most of the time, now goes up to one bar below the 100 mark and stays there which is where it should be.

So it needed doing.

 

[hi_flyer437]

Is it an easy job on the W211? I've noticed that my 270CDi is sitting at around 60 on its regular run to Heathrow. Might try and get it done tomorrow if MB have one in stock and it's not too tricky a job.

 

[pdd]

Is it an easy job on the W211? I've noticed that my 270CDi is sitting at around 60 on its regular run to Heathrow. Might try and get it done tomorrow if MB have one in stock and it's not too tricky a job.

It's worth doing - it should be sitting at about 90. If nothing else it will help fuel consumption.

There are instructions somewhere on here for changing:

http://www.mbclub.co.uk/forums/engine/87311-how-change-thermostat-om648-w-s211-320cdi.html

The 270 is probably much the same although some seem to have an additional push on hose at the bottom (it is a slightly different part number) which on the 320 version is blanked off.

Remember to have some anti-freeze on hand to top up with - most of the loss is from the head rather than the hose - and after replacing it give the car a run to get the thermostat open after which you will probably have to top up again.

 

[DJFarmo]

I'm glad I've come across this thread. I noticed that my fuel economy on the motorway has dropped from 40+ mpg in September to about 34 mpg in December in similar driving conditions. I only got the car in August and since observing the drop in fuel economy I have noticed that the temp gauge never gets above 60c, even on journeys of 2 hours or more. I guess the thermostat is the most likely cause.

Thank you to 'pdd' for posting the 'how to' link and to everyone else for their input. Given the relative inexpense of a new thermostat from MB, I think I'll pick one up and have a go at changing it myself. I'll report back on whether it resolves my fuel economy issue.

 

[fah320]

Mine was 60 even in summer when driving downhill. I changed the thermostat and it is always above 80 now, even downhill at minus outside temparature.
However 12 mile journey is not enough to get the temparature to 80. Everymorning I drive 13 miles and the temparature is around 70 when I arrive. So to make sure about the thermostat failure you should try longer runs...

 

[DJFarmo]

I replaced my thermostat on Saturday and it has cured the temperature and fuel economy problem I had. Changing the 'stat was easy thanks to the 'How To' guide by 'Corned'.

My car engine water temperature now rises to around 90c as expected and stays there - previously it rarely went above 60c and tended to fluctuate too.

At the weekend I drove from London to Worcester (where I changed the 'stat) and back to London again. The traffic and driving conditions were very similar on both trips; fuel economy driving to Worcester = 35.5mpg; driving back to London = 41mpg.

 

[LudoCLS]

high temp

After thermostat replaced temperature reach 98?/100 on my 320cdi, all work fine but I feel that engine smells like its too hot...
any ideas whats wrong?...
thanks

 

[LudoCLS]

and b4 I replaced thermostat temperature reached no more than 60

 

[Dieselman]

98-100c is too hot, it should be 87-90c.

It won't harm it, but it is hotter than standard. Did you get the correct thermostat?