OM651 Engine - 50k Miles - Do they all rattle very slightly from cold?

[MinionBob]

I have a 50k, 2012, OM651 engine that has a very, very slight rattle (1-2 secs) from cold. Nothing when warm.

Do they all do this?

I have seen a few posts and heard videos about cold start rattles on these engines indicating a faulty timing chain tensioner. Tensioners are about £80-£100, genuine Mercedes.

I'm happy to replace but if all these engines have a very, very slight rattle from cold, and no tensioner is needed, i'm throwing time and money away!

Advice/thoughts all welcome. Thanks in advance

 

[garethbevan59]

Unfortunately this is the dreaded timing chain, they stretch and could be fatal if not changed soon. I had to recently change my chain at my local Merc indie as it's not diy, if you plan to keep car get it replaced if not send it down the road before it snaps

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[malcolm E53 AMG]

Do you switch off the stop/start when you start the engine that will help its longevity if you forgive the pun. I wouldn’t worry too much you will know when the car needs either a new tensioner or sprockets and chain the rattle art start-up will be quite audible

 

[matthew k]

It does seem odd the way that Mercedes and BMW like to place these chains at the back of their 4 cylinder engines. The same engines that seem to eat chains, generating post sale revenue on parts and considerable labour costs.

BMW produced the M47 engine from 1998 to 2007, the chain was fine, 200,000 miles + with no problems was common. Then it's successor is released the N47 with the chain located at the back, and well you can guess the rest.

 

[onefortheroad]

My c250 is on 71000 and silent. Keep the oil good helps and turn off stop start.

 

[Gazwould]

It's all to do with silly EU safety laws and the great
( not) pedestrian likelyhood of their bodies becoming part of the mechanism.

Nice 7.5A fuse to pull right next to the auxiliary battery.

Stop Start and long service intervals are killers.

 

[onefortheroad]

Cant seem to find the fuse in mine . It's a 2015 w204 ?

Argh found it hiding at the rear. Many thanks.

 

[Wighty]

Cant seem to find the fuse in mine . It's a 2015 w204 ?

Argh found it hiding at the rear. Many thanks.

So does pulling that fuse manage to permanently remove the stop/start ?

 

[onefortheroad]

So does pulling that fuse manage to permanently remove the stop/start ?

It does on the w204 marra

 

[LostKiwi]

It's all to do with silly EU safety laws and the great
( not) pedestrian likelyhood of their bodies becoming part of the mechanism.

Nice 7.5A fuse to pull right next to the auxiliary battery.

Stop Start and long service intervals are killers.

It's actually more to do with lowering bonnet lines for better aerodynamics.

 

[Dean Fletcher]

My c250 is on 71000 and silent. Keep the oil good helps and turn off stop start.

Top trumps. My E250 is on 136k and going strong.

 

[davidsl500]

What else stops working if the fuse is pulled?

 

[onefortheroad]

What else stops working if the fuse is pulled?

Nothing on mine.

 

[Gazwould]

No issues .

Must be 5 months now .

 

[Exp21]

Hi. I have a dilemma. My w204 om651 with 80k miles has done timing chain rattle two times till now. One after 15 days of stop, the other one when I cold started the engine in a not flat park. The other times I start the engine I can hear the engine noise being stronger, but it's not a rattle. It's only a louder noise for 2-3 seconds. I know probably the chain is already elongated enough, but mechanics don't tell things as they are. What should I do? Continue like this hoping that it won't damage camshafts or prevent and spend another fortune? Honestly I don't believe in the option of replacing only the tensioner. In my opinion wear has already occurred in the chain, it would be a waste of money doing half the job.

 

[MinionBob]

If you have only had a rattle twice, it is unlikey to be a chain on its way out as it will rattle at every start; you mention that one of these times was after 15 days of being stopped - it might have been that all the oil drained out of the tensioner.

FYI a tensioner change is under 1hr job on my auto.

I think you should start worrying if you get a noticeable rattle at every startup

 

[Exp21]

Hi and thank you. I was thinking the same thing, probably the tensioner had to recharge the right oil pressure. But I notice that even on hot/warm engine when I start it I hear a light ticking for the usual 3 seconds. I'll ask for the only tensioner replacement cost, then I'll evaluate. Anyway I think that an even slightly elongated chain leads to nothing good. Wear in the sprockets teeth causes iron dust to contaminate oil. If you want to keep the car for long time it's an issue that has to be repaired at birth (in my opinion). I'll let you know if I have news about the issue

 

[MinionBob]

Mine too has a 'light ticking' but have come the conclusion it is the vaccum pump - the timing chain is a more of a harsh rattle.

I don't actually think that chain/sprocket 'wear' in itself is a problem, as all parts of an engine wear, but it is the knock-on consequences that are; inability for tensioner to accommodate wear, slapping chain takes out tensioners, jumps off sprockets, etc. these are the problems really.

cheers

 

[Exp21]

Mine too has the vacuum pump ticking. Do you know if starting the engine without pushing the brake pedal is enough to exclude the pump ticking? I was always asking myself this thing. I'm quite sure my ticking is from chain. It's like chain for the first 3 seconds doesn't have the right tension, so engine noise is stronger and then stabilizes to normal and quiet. Thanks again. Cheers

 

[MinionBob]

Not sure - mine is an auto so I have to press the brake to be able to start it.