dieselkiki

Timing/oil pump chain

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Hi folks, :) There's some of you who did replaced a timing chain or the oil pump chain on an OM660 CDI??? :unsure: The engine on my 2006 smart CDI make a noise of "slack" chain in the front cover. I thought that was normal but when a friend come at home yesterday with his smart... her engine was very quieter than mine!! Since I understand it I'm very worried about a timing/oil pump chain failure. :( So, I dont want that one of that chain break on the highway. I want to removed the front cover to inspect both chain. Somone have some information on the procedure, torque of the bolts (crank damper, front cover, vacuum pump etc...). So, any help will be welcome!ThanksDom

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I know not of what I speak, but (there always is a but) it's election time so why should I be different from our leaders?Again, I don't know if it's the case with the Smart engine (and here's the but again), but on a Merc diesel one sets the camshaft pulley at zero then if there is no chain stretch the crankshaft pulley will line up with its zero point. The the amount that it is off is the degrees of stretch. It's been a while, I think that four degrees of stretch is starting to be bad and at seven, it's about to break. Oh, I just realized that you're a stone's throw from me. Who do you use for servicing? Also, for what it would cost, I would go to Rive-Sud and have it diagnosed. It would be a $50 well spent.

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I am glad you noticed this sound now, before it is too late. I think the dealer would charge about $1000 for the job. The engine has to come out.

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I'm confused.... is this a "normal" thing on the list? I thought only timing BELTS need to be replaced.... Cost me (including waterpump) $1400 on my Eurovan...

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As a rule, the timing chain problem is due to the plastic tensioner breaking, then the chain slaps around until it too breaks.As long as the tensioner holds up there should be no chain problem for the life of the engine. An easy check is to feel the chain tension through the oil filler cap with a slim screwdriver or other thin metal rod. There should be no perceptible slack on either side. The oil pump chain can't be checked without dropping the pan. Both chains are sensitive to oil quality, as is the rest of the engine. Lots of oil changes! Turbos are hard on oil, diesels are hard on oil. 8K km is pushing it for maximum engine life, 5-6K would be better.

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If you ride a bicycle it is easy to know how much a chain can stretch, especially because a bike chain is a simplex (as opposed to duplex) chain, just like on the smart. I think chain stretch could also be an issue with valvetrain failure if it gets extreme, but usually the tensioner could take care of the slack. I asked TPM about prophylactic chain replacements and they are not sure whether it's worthwhile or not, even at 200K km. But if the chain is noisy now, it is time.

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Timing chains only last the life of the engine in terms of warranty or dealer terms...chains will not last the life of an engine in normal service where an engine lasts 20 years or many hundreds of thousands of kms. The chain is subject to some hard use on the cdi, I have seen an engine apart and it was filthy inside the chain cover, lots of debris the size of a finger nail just sitting inside the cover, black carbon stuff hard and flakey. I would guess the chain life to be around 200kms, but the plastic shoes on the tensioner/guides might not last that long, recent plastic parts on german engines are only lasting 6-8 years and 100-200kms. We see lots of cam adjuster shoes breaking on VW/Audi gas engines, lots...but diesels don't usely have the heat cycling that gas engines have. I think frequent oil changes are a big factor with the cdi staying clean inside, the cars are just getting old enough now for the plastics to degrade and show problems, but maybe oil changes or quality was a factor and the chain is simply stretched to far. Make sure the cogs/teeth are still good!

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Same as a bicycle the rollers inside the chain wear down and the chain is said to have "stretched".On a bike keep your drive train clean, use the proper lube and your chain will last a lot longer.On the smart change your oil/filter at least as often as MB recommends or more if you desire and it alsowill last longer...

Edited by lebikerboy

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As a rule, the timing chain problem is due to the plastic tensioner breaking, then the chain slaps around until it too breaks.As long as the tensioner holds up there should be no chain problem for the life of the engine. An easy check is to feel the chain tension through the oil filler cap with a slim screwdriver or other thin metal rod. There should be no perceptible slack on either side. The oil pump chain can't be checked without dropping the pan. Both chains are sensitive to oil quality, as is the rest of the engine. Lots of oil changes! Turbos are hard on oil, diesels are hard on oil. 8K km is pushing it for maximum engine life, 5-6K would be better.

Thanks about it Alex. So, the timing chain look to be in good condition. No delay between the rotation of crankshaft and the rotation of the camshaft when I turn the engine foward/back. I take a long screwdriver to check the chain and it look to be ok. No loose. But the noise is always there and I can't see the tentioner. I must remove the damper pulley to remove the front cover. Some of you have already remove it?? So... I'll call to mercedes-benz rive-sud tomorow to now the cost of both chain, guides, sprocket and tentioner. I'll replace "ALL" by myself. It's very meaningless that a mercedes-benz diesel engine timing chain must be replace at 116000km. My old 240D run about 730000km with it original timing chain. I can't understand! Where's the reliabilty??? I'll replace it by myself cause Mercedes-benz mechanics are too incompetent and unprofessionals. They broke my car far too often. I can't be worse than they! <_< If somone have the torque of bolts etc... it will be very appreciate! N.B.: I'll try to make a video of the engine running tomorow. Thank you for your posts and sorry for bad vocabulary. :) Dom
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If the chain is tight, it shouldn't be making noise. Are you sure that is the cause of the excess noise? No point doing all that work if it isn't the problem!What else could it be? Lifters? External? Air leak? Do some more investigation before committing to this.

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N.B.: I'll try to make a video of the engine running tomorow.

I have been meaning to do the same as my smartie is getting pretty tick-tick-ticky too. I think it's more like valves or lifters rather than timing chain. Maybe I'll try for it tomorrow and we can compare!Bil :sun:

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Same as a bicycle the rollers inside the chain wear down and the chain is said to have "stretched".

They do that but they also do stretch too. The distance between pins in a chain is exactly 1 inch and I have seen some 10,000+ km bike chains with 10% extra length between pins! So I am certain this happens on the smart's oil chain and cam chain too.

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Chains don't "stretch".They most certainly wear, extra clearance in all those holes and pins makes the chain longer indeed, but if you measure any one link it's exactly the same dimensions as new. Except in hole diameters! You do measure the length of a worn chain to determine if it needs replacement, a rule of thumb in industrial chains is 1/4" per foot is acceptable.BTW, a badly worn chain won't fit a sprocket tightly anymore. If there is no slack on either side of the chain the tensioner is probably fine, if you can't find slack in the middle of the sprocket the chain is OK. Even if a worn chain is pulled taut around a sprocket due to chain wear all the tension is taken by 1 or 2 teeth on each side and in the middle the chain can be lifted off the teeth a bit. Best to repeat these tests with the chain in several locations.Lacking either of these symptoms I suspect the noise is caused elsewhere.

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Could be your lifters are getting old (hyd elements in mercedes speak, under $20 each), they tick away when worn, or maybe you have bad fuel? Is the noise around for the last few tanks or just recent? Many things can cause a diesel to run differently from another, injectors, fuel, oil, lifters, chains, air mass meters, clutch adjustment, leaking intercoolers, worn turbos etc. Very few mercedes diesels got away with the original timing chain, saw many jump or break when I was a coop student working on diesels, usually before 400kms. That was awhile back now...

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Could be your lifters are getting old (hyd elements in mercedes speak, under $20 each), they tick away when worn, or maybe you have bad fuel? Is the noise around for the last few tanks or just recent? Many things can cause a diesel to run differently from another, injectors, fuel, oil, lifters, chains, air mass meters, clutch adjustment, leaking intercoolers, worn turbos etc. Very few mercedes diesels got away with the original timing chain, saw many jump or break when I was a coop student working on diesels, usually before 400kms. That was awhile back now...

- Injectior # 3 are just replaced- Turbo & intercooler are 1 year old - air mass meter (witch one??? There's no air flow meter on smart CDI, sorry.)- Clutch ajustement are done at each oil change = okYou know, I'am a 10 year diesel mechanic and I have a good idea of what a bad injetor, turbo etc... do. I'm almost convinced that one of the 2 chain (tentioner/guide) are the noise source. I just want to knew if somone had removed the damper pulley and the timing cover on a OM660. I need the torque, the procedure and if there is someting to be careful when we do that kind of job. Could somone give me this information? That's all what I need at the moment. Thank you. I just called to mercedes-benz Rive-sud to know the prices of the parts I supposed to be failed. It's look like this:- Timing chain = 95$- Timing chain sprocket (cam) = 78$- Timing chain sprocket (crank) = 44$- Timing chain tentioner = 66$- Tentioner guide rail = 23$- Timing chain guide = 22$- Front crank seal = 14$- Dip stick o-ring = 2$- Oil pump chain kit (2 sprockets, chain, tentioner, spring) = 200$I hope I'll dont need all of them. <_< Dom

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Chains don't "stretch".

Oh yes they do! I should have kept my old 15000 km Rohloff chain from my bike to show you, the distance between pins was 10% over the 1 inch original spacing. The pin holes were not oblong, it was not wear (if the holes were oblong the pins would have fallen out and the chain would have soon been in pieces, it was the metal of each link that had stretched by the 10%.

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Dom, if you are going to do this work, you probably should buy all that stuff and do it......

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Dom, if you are going to do this work, you probably should buy all that stuff and do it......

I'll begin to remove the timing cover to take a look at chains and tentioners before wasting all that $$$. Because most of that parts are not refundable. :rolleyes: So... I'm not realy satified of my "smart" product. <_< Bad service, expensive maintenance fees, bad reliability... I'm vexed. :angry: I'll probably post somes pictures when I'll open the engine. Thanks for all. ;)

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Chain wear and care evokes never ending discussions, especially for new bicyclists who are not happy with this dirtiest of bicycle parts. This leads to the first problem, of whether there is a best (and cleanest) way to care for a chain. Among several ways to take care of a chains, some traditional methods are the most damaging while others work to prolong useful life.A myth that is difficult to dispell is the story that grease on a new chain, fresh out of the package, is not a lubricant but rather a preservative that must be removed. This piece of bicycling myth and lore thrives despite its illogic.Riders often speak of "chain stretch" a technically misleading and incorrect term. Chains do not stretch, in the dictionary sense, by elongating the metal by tension. Chains lengthen because their hinge pins and sleeves wear. Chain wear is caused almost exclusively by road grit that enters the chain when it is oiled. Grit adheres to the outside of chains in the ugly black stuff that can get on ones leg, but external grime has little functional effect, being on the outside where it does the chain no harm.The black stuff is oil colored by steel wear particles, nearly all of which come from pin and sleeve wear, the wear that causes pitch elongation. The rate of wear is dependent primarily on how clean the chain is internally rather than visible external cleanliness that gets the most attention.Only when a dirty chain is oiled, or has excessive oil on it, can this grit move inside to causes damage. Commercial abrasive grinding paste is made of oil and silicon dioxide (sand) and silicon carbide (sand). You couldn't do it better if you tried to destroy a chain, than to oil it when dirty.

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The holes in the outer links don't wear, the pins are a tight fit and peened in place so no movement there. It is the pivot point on the inner links that wear. Steel doesn't stretch by 10%. Period. Steels vary somewhat in properties, but generally reach their elastic limit at less than 2% elongation. Once you reach the elastic limit they stretch to the break point with very little additional strain, so in practice you never come close to the elastic limit unless you want certain catastrophic failure with only a slight overload. Certain fasteners with very precise installation procedures are meant to enter the elastic limit zone, but only once! Sorry, Mike, with all due respect (a lot) but you're off on this one.

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@Mike: did you "just" have the Rohloff chain or also the speedhub?

It was bought in 1992 and on my Raleigh Super Course with normal derailleurs for over 10 years (bad me!), no speedhub.

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