E250 temp.......... head scratcher

[john campbell]

Looking for some advice please......

My 2012 e250 temp gauge seems to struggle and only reaches 80 after a 12 mile run with average speeds of 30 and 40 mph driving. This is giving me an average of 27 to 31 mpg and i was getting around close to 48mpg in the summer. I bought a new thermostat from the dealers the other day and fitted it but this has made no change at all. Today i gave it a run on a motorway for a few miles and it got up to temp so i pulled into the services and let the engine tick over for around 15 mins and the temp dropped down to 80 again. Is this normal because every car i have owned (30+ cars) has never done this unless the thermostat is shot.

Any help is much appreciated.........

 

[CowleyStJames]

I would guess air block. Bleed again, You Tube bleeding procedure to do it correctly

 

[ajlsl600]

That or,if electronically controlled ? I have heard some are ? There is issue with sensor ,system that opens closed it.
Me, I would try some blanking off of part of rad to see if that improves things.

 

[M80]

Same with my Viano.
New stat from MB Newcastle is actually a bit worse than was. My consumption still seems acceptable, it being winter and my journeys being shorter and sporadic.

Previously would rise to 92, and drop to low 80's while coasting. Now 'eventually' gets to 98 / 100 and drops even lower than before.

A bit of reading and the engine temperature has a design of 70 - 100. The stat has 2 connections, one temp reading, t'other is for opening compensation from the ECU I believe. ECU sees more power delivery and opens the stat more.
In truth it seems to over compensate and not close enough to keep warm imo, but I'm still learning about the 651.

There is also a coolant pump change over valve, this was changed on mine last December prior to my ownership, I've yet to understand the purpose.

Earlier more simple designs would run at a near constant 85, bliss.

 

[john campbell]

Thanks for the help...........

Mine does have the electronic controlled thermostat and I bought it from merc Sunderland so it should be working correctly. I just find it odd that the engine won't run at full temperature through the cold months when you would think that most other engines would. Sounds like I'm looking for a problem that can't be fixed as it's designed to be like that.

 

[john campbell]

That or,if electronically controlled ? I have heard some are ? There is issue with sensor ,system that opens closed it.
Me, I would try some blanking off of part of rad to see if that improves things.

It comes as a complete unit with the new sensors in it mate. You would think replacing the whole lot would sort it out but I guess not on a Mercedes...........

 

[ajlsl600]

It would,nt surprise me. If you buy assly n fit it it then dont work properly unless brain told of replacement ? Coding ? Thus trying to force you into dealers.
Way things goin one will need the wheels coding to the car !!

 

[john campbell]

I also thought about the coding back to the car but the dealers told me it's just plug and play so that's what I did but I'm doubting it myself now. It just does not make any sense why they would design the car this way because running a engine cold would surely cause them to use more fuel like mine is and others are saying the same.

 

[ajlsl600]

To be honest I would think dealer likely right.? But did anyone check fault codes ? Its still possible that signal to open/close statt more is faulty ,even possible that this is origional problem un resolved. Has this car been anywhere near a benz update ?

 

[john campbell]

Checked myself for faults as I have icarsoft scanner and also used snapon and Delphi but no faults and the live data matched the temp gauge in the car just about. As for Benz updates it's never been in to a dealers for anything since it had 11k on it and it's on 66k now. I bought the car with 47k on it from a Russian woman who had it from New and anything it's needed since has been done by myself as I'm a machanic by trade. Might give merc a call on Monday to see what updates have been missed on the car and go from there.

 

[ajlsl600]

Was just asking. Take advise before doing any Benz updates. A lot of info on here. Personally, I going noweher near any updates until/ unless not possible to avoid..
If yr motor does not reach design temp at design point you have Stat or control of Stat issue, having changed Stat and removed all air and confirmed design temp and point that pretty much leaves control of Stat, no?
How does heater behave?

 

[john campbell]

The heaters melt the skin off your face and that's why I find it odd. It just doesn't make any sense to me so I will try and find someone who has star in my area and see if that will show anything. I don't really want a trip to the dealers if possible mate because of the stuff I have been reading about the updates Mercedes have been doing to people's cars. My car falls into the band that has the emissions problems so I don't want them messing around with the car to cover up there cheat on the ecu.