MB OM651.. out of ideas

[jeepmerc]

Hi all,

I have a Jeep Compass that is using a MB OM651 2011 engine (OM651.925 I believe - paper style cartridge filters). The problem I am having is a timing chain rattle on start. Its not a new problem But I only really noticed it after getting the car and doing the first oil / filter change. Judging my oil the previous owner didn't take care of it.

- If drive the car and get it warm with a longer drive, then leave it some hours, I can almost guarantee I will get a timing chain slap / rattle on start. It lasts 2-3 seconds But doesnt sound at all good and I think more than just "nature of hydraulics" (as in, turns heads in the street noise)

- If I just start the car, let it turn over 15-20 mins or just do short 10 min driving runs then leave it some hours (or even days..or even weeks..) and turn on, I get no rattle or chain slap or at the most 1 second or so if its been sitting a very long while.

In any scenario, once started it goes like clockwork with no chain noise. I had a Merc engine specialist take a quick look and "it all sounds good" once running.

I would have said chain stretch But then I assume it would always rattle on start regardless..

What I have tried:

- Changed oil a few times (Castrol Magnatec 5w30)
- Changed filter with changing oil (Mahle OX153/7D2)
- Motor flush (LiquiMoly) - didn't see any sludge, plastic or bad stuff. just dirty oil
- Took a gamble on some LiquiMoly Ceratec oil additive having read the reviews
- Talked to a dealer who advised there had been a few revisions of the chain tensioner. I bought the latest revision (genuine Merc) and changed out the original (.. not a fun DIY job at the rear of the motor behind a heat shield). The holes are larger than the original which I assume helps oil in faster to build pressure But it looked the same length.

Changing the tensioner improved things from always slapping on cold start to this occasional slapping after driving a distance.

At this point I dont know what todo - changing guides and chain is an engine removal job and not really worth it. Not sure that would fix it even..

I guess I could try yet-another filter and oil change But this time try a quality 0w30 with the idea it should flow faster and get the tensioner pressure up sooner to minimise the slap ?

My assumption is once the engine is getting warm and being pushed with longer driving, the oil is flowing and properly circulating and that somehow leads to pressure dropping faster once cooled down hence takes longer to get to the tensioner.

Could it be an anti-drain back value is stuck open somewhere ? not sure where to look for it even.. could it be something in the oil filter housing ?

Any ideas much appreciated !

 

[alexanderfoti]

Many of them do this, especially after an oil change. It does sound horrendous. If its bad, then the tensionser + chain should be changed and sprockets analysed for wear. However, unlike the 271 engine, I haven't heard of that many catastrophic failures of the timing system on this engine.

Putting the highest weight oil allowed will also quieten it down slightly and keep oil in places where it would otherwise drain down.

If it where me, I would ignore it. Doesn't sound nice but is probably not causing any damage.

 

[jeepmerc]

Thanks for your feedback - feels better.

Weirdly enough after the engine flush I assumed there might be some flush chemicals left in the sump so used a no-name cheap-as-I-could-find 5W-40 oil (not 229.51 MB spec) as a cleaning oil and ran it gently idling for a day or 2 before emptying and filling with up-to-spec Magnatec. I could have sworn that during that time I had no startup rattle at all but put it down to the flush doing its job. After filing it up again the rattle was back and of course sounds like near-engine death right after refilling first time.

It looks like 5w-40 spec is as high as I can go and still follow 229.51 spec. Its a high mileage engine and long past any warranties or dealer care so heavier weight might be good thing.

Not familiar with MB engines.. is it worth trying a quality 10w-40 even if off spec for extra protection or do I risk engine damage by going off spec ? weather here can go -15~ or so But then your only driving then if absolutely necessary and planning to drive it until it dies.

 

[turbopete]

it seems to be common on the 651 engine. there have been odd cases of chains failing. ideally the guides etc should be changed. this is the exact reason I refused to buy another MB when I was looking, as the ones I wanted had this engine in them.

 

[silestanix]

If it's a high mileage engine then there may be usual wear and tear, try it once and see how your engine performs. Engines do wear, how much and wear rate depends on operating conditions, operator, oil but more than anything oil change intervals.

Good luck.

 

[Steve@Avantgarde]

The chain guides also wear and rattle. Done a few of them. Essentially, you are looking at replacing the chain. Its not all that bad a job and the timing chain only drives the HP fuel pump and camshafts. Everything else is geared. You will need the special tools to lock the engine though.

 

[jeepmerc]

Mystery continued: if you park after getting the engine up to temp. wait a minute or two, start the car again and set it idle 10~ seconds then shut it off again then you can bet the chain rattle will be gone even if you leave it a couple of days or even a week. haven't tried longer. I assume it builds the hydraulic pressure and fills the channels and since its not then driven, the pressure is maintained sufficiently on the "tensioner side" so help on the next start days later.

Going to try a final engine flush, genuine Merc filter (wasn't much more expensive than the Mahle though assume its 100% identical product with a different badge) and Mobil 1 0W30 (vs.Magnatec 5W40) given it seems the preferred spec according to the oil makers for this engine. Would be counter to the logic that oil is draining But perhaps it helps build pressure faster and less heart stopping..

(p.s if you order a OM651 filter through a Jeep dealer it was 1/2 the price of the identical thing through a Merc dealer)

 

[Steve@Avantgarde]

I don't see how you think that an engine flush is going to help. Engine oil is so thin these days, even on diesels you will be surprised how clean engines are. As long as oil is specced to MB229.51 the oil is fine.

 

[ajlsl600]

Mystery continued: if you park after getting the engine up to temp. wait a minute or two, start the car again and set it idle 10~ seconds then shut it off again then you can bet the chain rattle will be gone even if you leave it a couple of days or even a week. haven't tried longer. I assume it builds the hydraulic pressure and fills the channels and since its not then driven, the pressure is maintained sufficiently on the "tensioner side" so help on the next start days later.

Going to try a final engine flush, genuine Merc filter (wasn't much more expensive than the Mahle though assume its 100% identical product with a different badge) and Mobil 1 0W30 (vs.Magnatec 5W40) given it seems the preferred spec according to the oil makers for this engine. Would be counter to the logic that oil is draining But perhaps it helps build pressure faster and less heart stopping..

(p.s if you order a OM651 filter through a Jeep dealer it was 1/2 the price of the identical thing through a Merc dealer)

does that tensioner have an oil feed and an o ringto keep the tension pressure, and it just leaks at times, seem to remember something like that on Aclass ,o ring change on tensioner piston resolved the matter . perhaps someone has picture of that in bits ,pts listing ...

 

[LostKiwi]

These engines have a reputation for chains
http://forums.mercedesclub.org.uk/index.php?threads/om651-diesel-engine.127811/

Note post #22.

 

[jeepmerc]

Thanks for the all tips.. the tensioner was brand new out the box.. I might have extreme bad luck and got a bad one But then it has improved things.. its torqued correctly and can't feel any oil. If it was leaking and slowly losing pressure then I guess after extended driving, then the chain should start slapping..

What I really don't get here: if the chain was stretched or the the guides were worn, then surely it would always rattle on a cold start ?

I have let the car sit idle nearly 2 weeks outside now in cold weather. Long enough to have lost pressure. It hasn't been moved. I start it up last night and no rattle whatsoever - runs like clockwork. I can rev it up and stress the engine. turn off and repeat a few days later and.. no chain noise whatsoever. Starts up first time, everytime.

If I now drive /move the car and get it up to temperature or even a short 10 min drive - flat road..nothing extreme, park it up and leave it a few hours or a day or so, I can almost guarantee a chain rattle. Sometimes much worse than other times. When its bad its literally as if there is no oil in the tensioner at all at times.. definitely not healthy (as if you just did an oil change and its empty).

Basically this all hinges on the car moving which makes me suspect something else.. oil level stays the same so I don't think its leaking.

Any other pointers to things I could check before I admit defeat and have to drop the engine ? would be a nightmare to change the chain and guides and have it come back..

Could the filter housing and /or the oil cooler possibly be involved here - perhaps something opens up in there depending on the temperature hence problem only surfaces when its been moved ? I believe the anti-drainback valve is in the housing assembly for example..

 

[Steve@Avantgarde]

I was only reading a TIPs document about timing gear bearings and lanchester shaft bearings being the cause of rattling on start up. It is likely your issue all along.

 

[J Eaton]

Thanks for the all tips.. the tensioner was brand new out the box.. I might have extreme bad luck and got a bad one But then it has improved things.. its torqued correctly and can't feel any oil. If it was leaking and slowly losing pressure then I guess after extended driving, then the chain should start slapping..

What I really don't get here: if the chain was stretched or the the guides were worn, then surely it would always rattle on a cold start ?

I have let the car sit idle nearly 2 weeks outside now in cold weather. Long enough to have lost pressure. It hasn't been moved. I start it up last night and no rattle whatsoever - runs like clockwork. I can rev it up and stress the engine. turn off and repeat a few days later and.. no chain noise whatsoever. Starts up first time, everytime.

If I now drive /move the car and get it up to temperature or even a short 10 min drive - flat road..nothing extreme, park it up and leave it a few hours or a day or so, I can almost guarantee a chain rattle. Sometimes much worse than other times. When its bad its literally as if there is no oil in the tensioner at all at times.. definitely not healthy (as if you just did an oil change and its empty).

Basically this all hinges on the car moving which makes me suspect something else.. oil level stays the same so I don't think its leaking.

Any other pointers to things I could check before I admit defeat and have to drop the engine ? would be a nightmare to change the chain and guides and have it come back..

Could the filter housing and /or the oil cooler possibly be involved here - perhaps something opens up in there depending on the temperature hence problem only surfaces when its been moved ? I believe the anti-drainback valve is in the housing assembly for example..

I have exactly the very same issue on a Jeep Compass I have recently purchased and ask the same question why does the engine rattle on start up after example 30 mile run and not a 5 mile run.

 

[turbopete]

I was only reading a TIPs document about timing gear bearings and lanchester shaft bearings being the cause of rattling on start up. It is likely your issue all along.

ive no idea how high the mileage is on the OPs engine but SURELY unless its been seriously neglected, engine bearing failure/rattling on ANY engine should be virtually IMPOSSIBLE nowadays (unless neglected, run short of oil etc)

apart from Subaru Impreza Turbos I cant think of the last engine I heard with a knock that had been properly maintained and run with the correct level of oil etc. if what you have read in the TIPs document IS the case, I wonder if there is something amiss in the engine design or lubrication system somewhere, as most MB diesels seem to be good for 500k miles if properly maintained.

 

[jeepmerc]

I have exactly the very same issue on a Jeep Compass I have recently purchased and ask the same question why does the engine rattle on start up after example 30 mile run and not a 5 mile run.

..finally. Thought I was the only one.

Changing the chain tensioner to the latest Mercedes model (has much larger holes which I assume allow the oil in faster on start) But its identical length helped somewhat But its not a complete cure. Getting at it is a serious pain in the butt and given its spring loaded, once its out, getting the new one pretty much requires a thumb wrench given you need to push and turn same time at the back of engine between fuel lines. Jeep / Merc will tell you it needs the engine removed and special tools But its doable with a lot of patience and swearing. PM if you need help.

What 100% works is.. after a longer run (engine temp in the middle seems to be the "trigger"), park up and turn off as you usually would. Wait a few seconds, ignition on again and rev the engine for a few seconds and shutdown = no more rattle next time regardless how long you wait. Even had the car not started for 4 weeks after this trick and it starts with no rattle every time.

Root of the problem is oil isn't getting to tensioner fast enough on cold start to pressurise it hence chain is flying around and probably mashing the guides.

Read somewhere there is an anti-drain back valve in the filter housing / oil cooler so might swap it out for a low mileage part and see if that does anything.

 

[Paul Goff]

..finally. Thought I was the only one.

Changing the chain tensioner to the latest Mercedes model (has much larger holes which I assume allow the oil in faster on start) But its identical length helped somewhat But its not a complete cure. Getting at it is a serious pain in the butt and given its spring loaded, once its out, getting the new one pretty much requires a thumb wrench given you need to push and turn same time at the back of engine between fuel lines. Jeep / Merc will tell you it needs the engine removed and special tools But its doable with a lot of patience and swearing. PM if you need help.

What 100% works is.. after a longer run (engine temp in the middle seems to be the "trigger"), park up and turn off as you usually would. Wait a few seconds, ignition on again and rev the engine for a few seconds and shutdown = no more rattle next time regardless how long you wait. Even had the car not started for 4 weeks after this trick and it starts with no rattle every time.

Root of the problem is oil isn't getting to tensioner fast enough on cold start to pressurise it hence chain is flying around and probably mashing the guides.

Read somewhere there is an anti-drain back valve in the filter housing / oil cooler so might swap it out for a low mileage part and see if that does anything.

......if I need help!!!!! I would need Largactil and a straight jacket Very well done sir!

 

[Bclass2018om651]

Hi all,

I have a Jeep Compass that is using a MB OM651 2011 engine (OM651.925 I believe - paper style cartridge filters). The problem I am having is a timing chain rattle on start. Its not a new problem But I only really noticed it after getting the car and doing the first oil / filter change. Judging my oil the previous owner didn't take care of it.

- If drive the car and get it warm with a longer drive, then leave it some hours, I can almost guarantee I will get a timing chain slap / rattle on start. It lasts 2-3 seconds But doesnt sound at all good and I think more than just "nature of hydraulics" (as in, turns heads in the street noise)

- If I just start the car, let it turn over 15-20 mins or just do short 10 min driving runs then leave it some hours (or even days..or even weeks..) and turn on, I get no rattle or chain slap or at the most 1 second or so if its been sitting a very long while.

In any scenario, once started it goes like clockwork with no chain noise. I had a Merc engine specialist take a quick look and "it all sounds good" once running.

I would have said chain stretch But then I assume it would always rattle on start regardless..

What I have tried:

- Changed oil a few times (Castrol Magnatec 5w30)
- Changed filter with changing oil (Mahle OX153/7D2)
- Motor flush (LiquiMoly) - didn't see any sludge, plastic or bad stuff. just dirty oil
- Took a gamble on some LiquiMoly Ceratec oil additive having read the reviews
- Talked to a dealer who advised there had been a few revisions of the chain tensioner. I bought the latest revision (genuine Merc) and changed out the original (.. not a fun DIY job at the rear of the motor behind a heat shield). The holes are larger than the original which I assume helps oil in faster to build pressure But it looked the same length.

Changing the tensioner improved things from always slapping on cold start to this occasional slapping after driving a distance.

At this point I dont know what todo - changing guides and chain is an engine removal job and not really worth it. Not sure that would fix it even..

I guess I could try yet-another filter and oil change But this time try a quality 0w30 with the idea it should flow faster and get the tensioner pressure up sooner to minimise the slap ?

My assumption is once the engine is getting warm and being pushed with longer driving, the oil is flowing and properly circulating and that somehow leads to pressure dropping faster once cooled down hence takes longer to get to the tensioner.

Could it be an anti-drain back value is stuck open somewhere ? not sure where to look for it even.. could it be something in the oil filter housing ?

Any ideas much appreciated !

Hi i know this is an old post. But im having same issues with b class 2018 om651. Its not high miles 60000 and i change oil and filter merc genuine. 3 times a year. It actually started the rattle as far back as it having 10000 miles on it but was just on very rare occasions. Strangely enough after i did first diy oil change. Ive allways changed all filter o rings every time. Its now at 60000 miles and does the chain rattle every overnight morning cold start. 3 secs then silence. Ok its prob time for new chain or at least tensioner. But i fear even when done the rattle will return. In a year or so. Because i think the real issue is what you have mentioned in your post. For some reason the oil in filter housing drains back into sump overnight. If i remove oil filter after overnite rest. Ok the oil runs back the minute you pull out filter and stem. But my filter is completely dry as if oil filter housing drained hours before. Not a sign of drips on filter. This just cant be right. My car never rattles after first start rest of day. So i one day stopped engine when hot. Removed filter fast. No oil in housing. As drains back when stem is pulled but oil filter was wet and dripping as oil just drained back at that point. I put filter back in. Start warm engine. Oil pump then has to refil filter. And guess what. 3 secs rattle. So why is filter draining back overnight. ??? Causing delay in feed too chain tensioner. Did you get anywhere with your cooler change as i viewed a you tube vid. ( oil cooler check valve leak ). Which shows a leak on a check valve on oil cooler. I wonder if this check valve is the real cause. Of failing tensioners. Being damaged due to start up with no oil in them ?

 

[Craig71]

Having the exact same problem with my W204 200 CDI. Tensioner, oil and filter changed and seems slightly better, but still get the dreaded rattle normaly when it's been stood over night but not always. Anyone found a solution yet?

 

[alexanderfoti]

Have you changed the chain?

 

[Craig71]

No not yet. Will be the next option if nothing else works. Just don't see how it can be so intermittent if the chain was stretched. Just started it a minute ago after being stood in the snow for 2 days and not a single sound or rattle, wierd.