Om660 Timing/oil Pump Chains

[DesignerDave 5]

Hello everyone, I just posted recently in the "introduce yourself" section of this forum, and I've put a poll in that post with a couple questions for the diesel Smart drivers out there.Just to bring the topic over here so it is in the proper section:I'm a professional mechanical designer and I have noticed most of the engine problems with the diesel Smart engine comes back to the chain and sprocket setup used on those engines. I'm putting together a new design that I hope will solve all the chain related problems these cars have. I've been racing motorcycles for many years and have dealt with the silent chain the Japanese like to use for the camshafts and I think that design will be much more suited to this engine than the bushing chain currently in use.I've already measured up most of the components and once modeled up I'll attach some images of the proposed "kit". I have my own machining equipment so it is just a matter of getting the right cutter and I can get some machined for use. I have a buddy who has an induction heater I can use for treating the tooth profile for hardness, so I think long life is not going to be a problem. Any feedback on this would be great! As I said in my other post, if I can keep more of the cars running longer, that would be awesome. The world needs more little cars!!Regards,Dave

[MikeT 747]

I like the idea, but it would be good to have an alpha test vehicle to prove out the design. Are you planning to do this? My 2005 car (black and green) has 245,000 km.

[bilgladstone 13]

Mike, I think Dave has a dead 2006 cdi he is rebuilding and will use the first kit on that one. Looking forward to pictures and further writeup as the project progresses!Bil

Edited October 5, 2012 by bilgladstone

[tolsen 630]

Bush chains are very common in timing and oil plump drive applications on diesel engines and not only limited to the OM660 engine in the Smart. There may have been a handful of chain failures at the most but is that cause for alarm? I think not especially as we still do not know what was the root cause for these chain failures.How do we ensure our chain drives remain in service and do not fail? Regular checks of oil level and oil & filter changes. Listen regularly to the chain drives for abnormal noise. Unfortunately, performing a visual examination of all of these chain drives is impossible unless engine is removed from the vehicle.

[bilgladstone 13]

Another thought: if we had a "silent chain" kit, would the sound reduction be sufficient to let us listen for and identify noises from the valve train etc to warn of other potential trouble?B

[tolsen 630]

It seems there are several mechanisms leading to chain failure;

1) Wrong or lack of heat treatment of sprocket. Here is an example.

Totally fubarred oil pump sprocket. All teeth gone. Looks like it was made out of cheese.

2) Loose sprockets.

Above oil pump sprocket appears to have worked loose and wobbled on the shaft. This resulted in broken chain. There was no mention of wobble in the thread where I found this photo but it is obvious judging by the shiny marks in centre of sprocket.

3) Broken guides. One Smart specialist (Smart Tecnic) recommends renewing the guides every 75,000 miles.

Broken guides galore.

[bilgladstone 13]

It seems there are several mechanisms leading to chain failure;

ALL of which would be mitigated or completely eliminated with Dave's new design!B Edited October 5, 2012 by bilgladstone

[DesignerDave 5]

Good points,Perhaps the sprocket is made from poor metal, or has not been hardened properly, this does seem to be the case. Still, that type of chain is weak and has known shortcomings that have been measured and documented in comparision with inverted tooth chains. I think the failures you are seeing can all be linked (Woah there is a good pun ) back to the same problem, which will hopefully be resolved. As far as the quiet nature of the inverted chain, this has two major benefits: 1. Less wear. Noise is the result of the chain hitting the sprocket teeth upon engagement, which over time kills either the chain, or the sprockets, or usually both.2. Less energy lost. It takes energy to make sound, so if there is no noise, it is more efficient. This is assuming both chains are giving off the same amount of heat due to friction.If you look up some other companies that have built inverted (silent, Hi Vo) chain setups to be swapped out from the stock roller chain setup they usually get a horsepower increase. Inverted chains have to be clean and well lubricated to have a long life, and this is the weakness of the chain. For a drive that will be exposed to the elements, like a motorcycle drive chain, it is not suitable. Should be interesting!

[tolsen 630]

Here is a guide to Silent Chain for those that may be interested:

http://www.tayloredge.com/reference/Mechan...ilentChain2.pdf

[MikeT 747]

I have always been suspicious of single row chains....all really good cars I've had in the past with chain driven cams have had duplex chains/double sprockets and they seem to last indefinitely (like: 400+ K km.) Early Renault 5s had single chains and they went to duplex chains in about 1980, and those later engines were far better and longer-lived.I suppose there's no room for such a chain inside the OM660 timing case.Inverted tooth chains sound interesting.

[houseofdiesel 9]

Maybe a case of simple adding more lubrication to the current chains? Each engine I have seen apart was filthy inside the chain case, huge chunks of carbon and a mess, like no oil flow to keep it clean. A new design sounds very interesting, hopefully it can be done within the parts costs of the current set up (as smart has pretty high retails on this stuff).

[shadejo 0]

I am most intrigued by the idea of a redesigned chain area as all of the failures I have been involved with (3 failed engines thus far) appear to trace the genesis of the failure to chain/sprocket damage and resultant metal particles circulating. I am convinced that the oil pump chain problem is particular is a case of poor hardening of the oil pump sprocket, and I have seen two sprockets that look similar to the photo earlier in the thread.I am also not a huge fan of simplex (single row) chains. In addition to the examples cited already they were used on all the early A series Austin engines (Morris minor, Sprite, mini, etc) , and were a source of problems, noise and occasional failure, especially in competition. Eventually a duplex setup solved the problems and pretty much eliminated the stretching and noise that was common on the smaller A series engines.I am very interested in the idea of an alternative. I would be willing to participate in some testing of a kit - I currently have one engine on the bench and will be rebuilding another this winter at some point. ( Can't resist getting back to my mech engineering roots but didn't have time to fabricate my own solution !)John

[DesignerDave 5]

Hey guys,So I ripped apart my engine last night, I was temporary stalled when I wrote my last few posts because I had to source a E-18 Torx socket. Although I couldn't actually see my oil pump drive at that time, I had assumed the failure of my engine was lubrication system failure, and as the images will show, I was right. What confirms for me the lack of quality of that sprocket is how perfect the driving sprocket still looks. I can only imagine the noise this car was making just prior to the turbo dying. What a shame. This is more like it. This chain and sprocket setup will hold up very well I'm certain. Now that I've pulled out all the parts, I can measure everything to put into CAD. More to come yet!Dave

[bilgladstone 13]

Very exciting, Dave! Can you tell from markings on the failed/rounded sprocket who makes it?Bil

[DesignerDave 5]

Hi Bil,The rounded off sprocket has a mercedes logo on it so OEM, but who actually produces it? I can only assume it is JWIS.I know someone on this forum managed to get into contact with them, now we have yet another example of the same damage... You should see my oil pump... it isn't pretty.Something I noticed in the one photo above with the broken chain guides, that engine has a dedicated line for lubricating the chains. My engine does not have that jet setup. I will have to make something that serves a similar function.My engine was half dismantled by the previous owner so perhaps what used to perform the same task was already removed, but I didn't see anything that resembled that setup. I do not have that threaded hole to attach such a fitting in that location.Although I couldn't tell by photos, the two chains are quite different in both pitch and width. The inverted chain I have will work perfect for the oil pump chain, which is the smaller of the two. I think a larger 3/8 pitch inverted tooth chain will work for the camshaft, though I would prefer to keep a metric system if possible. I started on this but wound up getting fed up with my cluttered garage which turned into a day long clean and reorganization operation. Though I haven't made as much progress on this, I sure do feel better when I'm in the garage. More to come! Have a happy thanksgiving (For all Canadians anyway)Dave

[bilgladstone 13]

I contacted IWIS and they say they do not make the oil pump drive chains or sprockets. We had in mind to ask them for superior quality sprockets but now you're working on an even better solution :thumbup:B

[MikeT 747]

Now that is interesting news, that the older engines don't have an oil jet for the chain, and the newer ones do.....and older in a relative way, because the cdi had been in production between 1999 and 2004 before we got it. So did the design change in model year 2006?? Do you have any VIN info on the engines you got, Dave?So far my 2005 seems to be doing OK without an oil jet (assuming it's not got one), at 245,000 km.

[bilgladstone 13]

This all highlights how very important it is to be religious (even... obsessive? yes, I think I might be that) about oil change intervals, always change the filter when you do the oil, and use the best quality, MB229.5-certified, fully synthetic oil you can afford. My choice is LiquiMoly's High-Tech fully synthetic.

Superior filtration can also be achieved with the addition of a spin-on adapter and the use of high quality canister filters. Like this Mercedes diesel engine OEM spec fleece filter from Mann.

...............

Also, a small amount of Cetane boosting and fuel system cleansing additive every tankful will help keep the top end clean. Like top-of-the-line LiquiMoly.

Hmm... seems to be a Made-in-Germany trend here. Oh well the engine is made in Germany by Mercedes-Benz, right?

B

Edited October 7, 2012 by bilgladstone

[DesignerDave 5]

Alright, I need someone to tell me what engine that is in that photo with the broken guides, cause the oil jet isn't the only difference between that engine and most of ours. It has... that's' right... a different oil pump sprocket. So if we can find out what year of engine that is, maybe we already have a better solution for the sprocket. Don't get me wrong, I would much prefer an inverted chain setup, but if the part already exists that will greatly increase the life of the engine without me having to do a bunch of custom work, well... I do have other projects that can be focused on too...If you look closely you will notice that sprocket has a ridge around the perimeter, whilst ours (A 660 181 00 12) does not. Different yes, but better? Well it can't be worse. Can someone confirm for me what engine is in that photo with the broken tensioner?Thanks!Dave

[DesignerDave 5]

Well, from hours of searching, and not sleeping like I really should be (it's 5 am!) I have determined the sprocket that looks different comes on the smaller displacement gas engines. I may be wrong there though.I found an image of a kit that has the other sprocket design, but I can't find a part number for the actual sprocket itself. I also notice the new hydraulic lifter dieselkiki observed seems to match the design used in the gas engines. Once again, this may be a case of the images I'm seeing online not matching what you are going to get, but so far this is what I have found.For what it is worth, take a close look at the photo with the chain guides destroyed. Look at that oil pump sprocket, it doesn't seem to have any wear at all, and that's with a destroyed tensioner.Very interesting

[DesignerDave 5]

I guess I have one more observation too, not only does this other sprocket have more teeth (28 vs the diesel's 25) but it appears that the chain is the same size on both the cam and pump on that engine shown (in the photo with the broken tensioners). Now this makes sense since the chain would only have to drive the camshaft rather than the cam as well as the high pressure pump. I can understand why they geared the pump slower on the gas engine since it typically runs at higher rpm than the diesel does. I wonder though if the slower speed would be an issue for lubrication or if the increased mechanical advantage would increase the life of both the chain and sprocket? I know of one way to find out!

[tolsen 630]

The picture is from a Roadster engine I think. 99% certain. You can tell by the oil cooler. Only the Roadster engine came with oil cooler as standard.

MB's part system seems to list two oil pump drives and only one timing drive.

http://www.neoriginal.ru/cat/mb/part__F_M_...450_402_/05_045

Perhaps someone in possession of a proper parts system can investigate further.

[dieselkiki 7]

There is something very strange in all these chain failure. I realy can't explain why some oil pump/timing chain/sprocket are worn out at 82000km and other OM660 engines traveled over 300000km with it originals chains and sprockets without any issue!! Irregular iron quality or bad oil quality or... I realy dont know.

Edited October 10, 2012 by dieselkiki

[bilgladstone 13]

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The unpredictable nature of these failures makes this upgrade a good candidate for a 150-200,000km recommended replacement!

I remember we had a high-mileage Dodge Omni in the family years ago as a first car for one of the daughters. When we took it in for inspections, mechanics invariably told us they were notorious for timing chain failures and even though it wasn't showing any signs at the moment they always recommended to replace the timing chain after 100,000 miles.

I'm thinking this engine should be treated the same way if you want to keep it running reliably for a long time.

Bil

[dieselkiki 7]

Bil... dodge omni have timing belt. The 1,7L volkwagen, 2,2L and 2,2L turbo from Omni GLH get belt too. That was the same for plymouth horizon, dodge rampage, tourismo and all other of that "beautiful" familly. What kind of mechanic you get?? :PSo, in my mind, a chain should normaly last for more than a belt liftime. Minimum 300000km! Mercedes timing chain are suposed to last for 500000km! Why the OM660 dont last as this?? It's not normal!

Edited October 10, 2012 by dieselkiki