C350 CDI om642 correct engine temperature?

[MrGreedy]

Get booked in with PCS in Horndean. They really know their stuff and are competitively priced.

 

[E55BOF]

Get booked in with PCS in Horndean. They really know their stuff and are competitively priced.

I second that. They'll change the 'stat and the temperature, the gauge reading, and your fuel consumption, will all return to normal.

 

[Richteo]

At least you now know of three 'specialists' you shouldn't take your car to. The reality is they didn't want the work rather than they didn't know what a thermostat is meant to do.

This thread may be of interest if you do have the thermostat with the heater element, but being a later car I think you possibly won't. Check on partsouq using your VIN.

I would also look at your turbo ducting. If you don't have the extra 'branches' obstructing the thermostat it is a simple job any garage should manage. If you do it is a PITA and I would recommend changing all the intake and ducting seals. Also a good time to do the fuel filter as the same stuff needs to come out.

For reference my 2012 cls 350cdi gives a dash-indicated 45mpg easily on my 30ish mile mainly motorway commute, and hovers just below 50 on longer runs with no real attempts to drive economically.

 

[philnewmerc]

Cheers all.

I plugged in icarsoft and watched the water and oil temps: On a long idle it went up to 81 deg water (~88 on dash), 75 deg oil, then ran it at 70 mph and it immediately started to cool to around 62 deg water (~67 on dash), 65 deg oil. In 50 mph roadworks i saw 58 deg water, 62 deg oil.

Hopefully MB main dealer will fix it

Really appreciate the advice

 

[OneForTheRoad]

Cheers all.

I plugged in icarsoft and watched the water and oil temps: On a long idle it went up to 81 deg water (~88 on dash), 75 deg oil, then ran it at 70 mph and it immediately started to cool to around 62 deg water (~67 on dash), 65 deg oil. In 50 mph roadworks i saw 58 deg water, 62 deg oil.

Hopefully MB main dealer will fix it

Really appreciate the advice

They will at a cost . The stat itself is around £120 off the top of my head .

 

[Gnasher141]

 

[MrGreedy]

Similar thread, but different engine. But I link to some other threads also on 350 CDI thermostat

Post in thread 'S213 E63 coolant temperature slow to warm up..'

Friday at 9:54 PM

My thermostat did this on my E350 CDI. There is a rubber gasket in mine, which starts to degrade. A thin slither of the gasket started to split (although I caught it before it detached), and this slither was getting caught between the two metal sealing surfaces of the thermostat, meaning the stat was wedged open a tiny bit by the wayward rubber. This resulted in the same symptoms you have.

Might not be this of course, and no guarantee that the thermostats are the same design. But something to look at. If it's anything like the V6 setup, the stat is relatively accessible on the top front...

• MrGreedy

• 

 

[sautah]

I have a few different cars a different brands. The general rule I have concluded is that the water temperature and the engine oil temperature are about the same when the engine is fully warmed up and normal road driving.

Yours is definitely either running cold or there is a sensor issue.

How about keeping it simple and carefully remove the expansion tank cap (cloth over it ) and stick a thermometer in there.

Or even an IR temp reader on the hoses etc.

Will give you a better idea of the actually water temp vs the dash gauge.

 

[E55BOF]

If Mercedes wanted their cars to run at 65 degrees, they would fit 65 degree thermostats... Without wishing to cast nasturtiums on anybody, could it possibly be coincidence that Mercedes fit 92 degree thermostats to pretty much all their cars, and the cars maintain more-or-less that temperature when running with serviceable thermostats? Anybody who actually believes that needs their bumps felt, expert or main dealer or not...

Alternatively, do 99% of Mercedes have coolant temperature sensors which show 65 degrees as 90? They mostly overread a little, I suspect, but not by that much.

If the running coolant temperature was showing as 90 degrees, and is now fluctuating well below this figure, and takes a long time to warm up, something has changed. It could be the sensor, but based on the experience of thousands of owners, including the OP, it's the thermostat; classic symptoms.

The Prosecution rests....

(The car will run OK with a faulty thermostat, for a time, but not at maximum efficiency, and the fuel consumption will suffer.)

 

[E55BOF]

How about keeping it simple and carefully remove the expansion tank cap (cloth over it ) and stick a thermometer in there.

Or even an IR temp reader on the hoses etc.

Will give you a better idea of the actually water temp vs the dash gauge.

I think the iCarsoft code reader has established that?

 

[philnewmerc]

Car goes in next Friday so I will return to the forum to update everyone after that.
Cheers
P

 

[ALFAitalia]

And of course thermostats dont dictate the maximum temp... only the minimum..... the fan switch temp dictates the max.

 

[ALFAitalia]

Sorry for poor quality pic... but this is my 350 CDI today... takes about three miles to get there at this time of year.... then does not move from that spot no matter how fast or slow I drive... which is how it should be IMO.