W212 E350 thermostat & heating problem

[liamski007]

Hi,

wonder can anyone offer their opinion on this. I think my thermostat is locked in the open position. On these cold mornings I struggle to get the car above 40deg, maybe 50deg in the town. Has anyone else experienced this. I presume that the thermostat is fully open and continually letting water into the engine from the expansion tank therefore not allowing the car to heat up to operating temperature of 80 or 90deg. This was not a problem a few months ago when the weather was warmer. It means I struggle to get warm on my 20 mile drive to work in the morning. I would appreciate any comments on this.

Thanks,

 

[MancMike]

I've got the same problem with my 3L V6. My 10 mile commute in the morning doesn't get the temp up to 90 anymore. I've resorted to having the heating completely off which helps (if I turn the heating on 5 miles in, it actually cools the engine a bit according to the dial!).

So I've either also got a faulty thermostat, or it's normal for a 3L engine when it's 1.5c outside.

I suppose you could check by starting on a cold morning, and looking for turbulence in the expansion tank?

Interested in answers too.

 

[mbenz1]

I'd put my money on the thermostat. But worth checking the coolant level and make sure there are no leaks in the coolant system before diagnosing further.

My dad's V6 CDI fully warms up within 10 minutes and stays dead on at 92C. Although he does keep the car garaged so that might aid warming up.

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[liamski007]

Mike - yeah I turn the heat off or low as well to help the engine warm up but it does little to help. I don't believe this is normal for this engine - that doesn't make sense. For one surely it's going to cause a bit more wear and tear on the engine as it is not fully expanded (being colder than it should be). Also a top end car with poor heating? surely not.

I don't mind changing the thermostat - it's not the end of the world but I wonder if it is the sensor, although I'm not getting the engine management light. I was half-thinking of siphoning some coolant out to bring to the minimum level but this seems absurd.

Hopefully someone may be able to help.

 

[liamski007]

mbenz1 - coolant level is fine........I'm quite meticulous about maintenance. Thanks for your comment though. I don't really think having it garaged would make much of a difference.

 

[55nick]

Thermostat needs changing the size of the engine should make little difference
If the coolant was leaking I think it would be overheating rather than staying cold

 

[HB]

Hi,

wonder can anyone offer their opinion on this. I think my thermostat is locked in the open position. On these cold mornings I struggle to get the car above 40deg, maybe 50deg in the town. Has anyone else experienced this. I presume that the thermostat is fully open and continually letting water into the engine from the expansion tank therefore not allowing the car to heat up to operating temperature of 80 or 90deg. This was not a problem a few months ago when the weather was warmer. It means I struggle to get warm on my 20 mile drive to work in the morning. I would appreciate any comments on this.

Thanks,

Thermostat.

 

[Dec]

As others say, replace thermostat with the correct part from an MB dealers.

Dec

 

[paul73mt]

thermostat +1 I had the same problem on mine took ages to get to temp then as soon as you turned the heater on the temp went down. 5mins to change and if your careful you will loose half a cup of coolant.

Genuine Mercedes-Benz OM642 Engine Cooling Thermostat A6422002215 NEW | eBay

 

[liamski007]

thanks to all who have commented here so promptly - the general consensus has confirmed what I thought.

 

[rorf]

Ditto thermostat

 

[PhilLinda]

Definitely sounds like thermostat. I had the same problem on my s212 E350. Replaced the thermostat and warms up perfectly now.


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[Kersidan]

+1 for thermostat. They wear out apparently! There are loads of posts on BMW forums relating to their 3.0d engines (they have two thermostats EGR and main) any problems with either and the engine will struggle or never get up to temp, I know from experience. This is BAD news for a diesel equipped with a DPF (i.e. E350 CDi) as it will not get to the correct temp to allow DPF regens and this will lead to a blocked DPF and a big bill. IMO you should change the thermostat and renew the coolant/antifreeze at the same time. Use genuine MB parts, thermostat is about £130 from MB Newcastle, they have an Ebay shop.

My E350 Cdi runs around 90C but I'll be changing the stat next year as preventitive maintenance.

Mark

 

[mbenz1]

+1 for thermostat. They wear out apparently! There are loads of posts on BMW forums relating to their 3.0d engines (they have two thermostats EGR and main) any problems with either and the engine will struggle or never get up to temp, I know from experience. This is BAD news for a diesel equipped with a DPF (i.e. E350 CDi) as it will not get to the correct temp to allow DPF regens and this will lead to a blocked DPF and a big bill. IMO you should change the thermostat and renew the coolant/antifreeze at the same time. Use genuine MB parts, thermostat is about £130 from MB Newcastle, they have an Ebay shop.

My E350 Cdi runs around 90C but I'll be changing the stat next year as preventitive maintenance.

Mark

Glad to hear the problem is sorted. I bet she warms up in a tick now! These Mercedes CDI V6s do warm up quick - I wish the 220 CDIs were the same in warming up.

IMHO changing a thermostat yearly as preventative maintenance means OCD to me These fail after some time meaning they do have a few years lifetime normally speaking. Just keep an eye on your engine temp behavior and any changes in it would mean a potential thermostat issue but I'm sure that day is not near yet. But it's your motor so your call. Enjoy

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[Kersidan]

Glad to hear the problem is sorted. I bet she warms up in a tick now! These Mercedes CDI V6s do warm up quick - I wish the 220 CDIs were the same in warming up.

IMHO changing a thermostat yearly as preventative maintenance means OCD to me These fail after some time meaning they do have a few years lifetime normally speaking. Just keep an eye on your engine temp behavior and any changes in it would mean a potential thermostat issue but I'm sure that day is not near yet. But it's your motor so your call. Enjoy

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Apologies if I misinformed. I'm not saying that you should change the thermostat anually. They do 'go off' over a period of time. My E350CDI is a 2011 and I'm considering doing a stat change next year as it hasn't been done yet i.e. for 5 + years. Keeping an eye on the engine temp to see if it's coming up to temp quickly is the best way. The E350 CDI does normally warm up quickly for a diesel.

Mark

 

[zipdip]

One small suggestion when you buy a new thermostat check to see if it is working,I know quaity has gone up in recent times but a few years ago there were a lot of new dodgy thermostats around just pop the new one in a pot of water and heat it up spoon it out and it should have opened.

 

[Avnt]

What temp is classed as acceptable on the 350 engine? 80-90?


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[mbenz1]

Apologies if I misinformed. I'm not saying that you should change the thermostat anually. They do 'go off' over a period of time. My E350CDI is a 2011 and I'm considering doing a stat change next year as it hasn't been done yet i.e. for 5 + years. Keeping an eye on the engine temp to see if it's coming up to temp quickly is the best way. The E350 CDI does normally warm up quickly for a diesel.

Mark

Apologies mate my bad - As I'm on my smart phone I can't tell who the OP is and thought that was you, hence my reply to your quote. I was under the impression the OP had got the new thermostat fitted and solved the problem.

I see what you mean. Yes it's a good idea to change the thermostat given the age of it. Just out of interest, how long does your 350 take to warm on a winter day?

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[mbenz1]

What temp is classed as acceptable on the 350 engine? 80-90?

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General rule of thumb is anything between 80C to 100C although modern Mercedes diesels should sit around 80C to 90C. I have heard 92C is the correct temp for the V6 CDI but not fully sure about this - my dad's S320 CDI sits exactly at 92C and stays there so it must be the correct temp.

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[Kersidan]

Apologies mate my bad - As I'm on my smart phone I can't tell who the OP is and thought that was you, hence my reply to your quote. I was under the impression the OP had got the new thermostat fitted and solved the problem.

I see what you mean. Yes it's a good idea to change the thermostat given the age of it. Just out of interest, how long does your 350 take to warm on a winter day?

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I've never checked it properly but I often drop my better half to the station first thing in the morning that's 4 miles away and the car is certainly up to temp by then, even on a cold morning. If the stat is good they seem to warm up quickly for a diesel.

Mark