Om651 - Chain vs Tensioner

[Notamech]

Hi All

I recently bought a 2013 E220 CDI with 67kmiles on the clock super clean car with almost full main dealer history. Only the last service was done by the car dealer that I bought the car from so im guessing they used a local indy and just changed the oil & filter.

I don't drive the car too much and its our 2nd car primarily used for long trips and outings rather than in the city. We have another petrol small car for those kind of short trips. That being said im not sure how the car was used before I bought it.

Recently I noticed that if i let the car sit for over a week, when i first start it up i do get the dreaded chain noise for 3-4 seconds. But after having run the car for a bit if i let it sit for a day or 2 i dont get the noise on a cold start. So seems like it happens only when the car has sat for long and the tensioner has drained.

The question I have is, is this normal? Is it to be expected that the oil will drain out from the tensioner if the car is sat for long periods? Or is it a sign of the tensioner failing? Also given that the car has done only 67k and has been serviced regularly I was thinking of only getting the tensioner done rather than both the chain and tensioner as reading on this topic, it sounds like the chain shouldn't stretch if its been serviced regularly but the tensioners are prone to failure. Does this sound right? Should i just change the tensioner?

I got quotes from 2 MB specialist in northwest London and one quoted around £260 to just do the tensioner. The other one quoted close to £550 saying that the rocker cover needs to be removed and the cams locked i clarified i just want the tensioner done not the chain. They confirmed that to do just the tensioner they set the timing and lock the cams and that if I want to do the chain as well im looking at close to £1100 with them. They said others might risk it by not locking the cams we don't. It doesn't make sense to me that they would want to lock the cams just to change the tensioner as the crank or cam probably wouldn't move and the timing shouldn't change just the chain would become lose and tight in situ. What are your thoughts on this? Does the cam need to be locked?

Here is the noise I am talking about.

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[Jonesy161]

This sounds like classic tensioner fail, I did mine recently after having the same symptoms, it took me two hours and the new tensioner was £100 from Merc Glasgow. £260 doesn’t sound too bad to me, especially if your not confident diy.
I’ve never heard of locking the cams for a tensioner change but I can almost understand their logic.
Good luck.

 

[Notamech]

This sounds like classic tensioner fail, I did mine recently after having the same symptoms, it took me two hours and the new tensioner was £100 from Merc Glasgow. £260 doesn’t sound too bad to me, especially if your not confident diy.
I’ve never heard of locking the cams for a tensioner change but I can almost understand their logic.
Good luck.

Thanks so much for the reply. Its reassuring to know that im on the right track in deciding to change only the tensioner. Oil changes is as far as my DIY skills go. Id rather get someone who knows what they're doing to do it. Will get it done this month, im inclined to go for the £260 quote as from my limited understanding i think the risk of it jumping timing while changing a tensioner is very low and i guess this is how others normally do it.

 

[Jonesy161]

Just make sure that they use the updated Merc tensioner, there are quite a few non Merc available, but imho not worth the risk.

 

[Notamech]

Just make sure that they use the updated Merc tensioner, there are quite a few non Merc available, but imho not worth the risk.

Yes definitely. The merc specialist is quite reputed but will insist that they use genuine parts. Also given my car is a 2013 facelift model I thought it would already have the updated tensioner but i guess they go bad too?

Today I went to get a few quotes from non mercedes specialist indies as well as it doesn't sound like a super complicated job that needs specialist knowledge but strangely a couple of them insisted I do the chain as well. I find it hard to believe that the chain on a 67k well maintained car could have stretched. But perhaps its possible with start stop? Is there any way one can tell if the chain has stretched without actually opening the rocker cover? Read somewhere about diagnostics being able to give a clue through cam compensation values being greater than 5 degrees or something. Is this true?

Also before this started, I added a can of liqui moly ceratec i didn't have this issue before the ceratec. Could this have caused some change in the oil that results in it not holding pressure in the tensioner? I plan to change the oil along with the tensioner anyway as i dont want old oil in the tensioner but was wondering if i should give it a try before.

 

[Tonygw]

Not sure about the liquid moly but I am of the opinion that you shouldn't need to add this kind of additive if you change the oil regularly. Mines changed every 6K as a min.

I also had the dreaded chain noise at 86K on my 2012 S204 OM651 C250. I opted to get the chain and tensioner done at a total cost from my local Merc specialist indy of £700. Using only genuine parts.

I did this as I didn't want the hassle of chaining just the tensioner only to find it didn't cure the issue.

The Mechanic did say that the chain did seem to have "stretched" if thats the right term, and at certain revolutions of the engine (when done by hand) there was a small amount of slack in the chain.

I think, and this is just my opinion, that the start stop or short journeys is the main cause of the issue. The continued starting accumulates to wear on the chain even at lower mileages.

My local Indy looked after one W204 with the om651 which was on its original chain and it had done 400K miles! So it can be a bit pot luck or it could be the start stop.. who knows.



In your case it could well just be the tensioner. they can fail.
Let us know how it goes

 

[Notamech]

Not sure about the liquid moly but I am of the opinion that you shouldn't need to add this kind of additive if you change the oil regularly. Mines changed every 6K as a min.

I also had the dreaded chain noise at 86K on my 2012 S204 OM651 C250. I opted to get the chain and tensioner done at a total cost from my local Merc specialist indy of £700. Using only genuine parts.

I did this as I didn't want the hassle of chaining just the tensioner only to find it didn't cure the issue.

The Mechanic did say that the chain did seem to have "stretched" if thats the right term, and at certain revolutions of the engine (when done by hand) there was a small amount of slack in the chain.

I think, and this is just my opinion, that the start stop or short journeys is the main cause of the issue. The continued starting accumulates to wear on the chain even at lower mileages.

My local Indy looked after one W204 with the om651 which was on its original chain and it had done 400K miles! So it can be a bit pot luck or it could be the start stop.. who knows.



In your case it could well just be the tensioner. they can fail.
Let us know how it goes

Thanks for the reply. The indie I spoke with gave me an appointment for the end of this month (apparently theyre super busy) so i plan to get it done then. My original plan was to keep the car for 5 years in which case I would have got both done together but it seems like with ULEZ likely to expand to outer London next year there is a chance i might just have to sell it in which case i dont want to have spent too much on it. I also changed the oil myself this weekend so lets see if the tensioner is able to hold in the new oil when its sat for long. If not il change only the tensioner.

 

[Notamech]

Another justification I read on another forum on why I should do only the tensioner now, which made sense to me, is that all chains will stretch a bit with age. Thats normal and expected, else we wouldn't need a tensioner. The reason to do only the tensioner is that the chain probably hasnt stretched beyond the acceptable limit else it would display symptoms like slapping rattling etc most of the time and not just once in a while when the tensioner has lost pressure, that is clearly just the tensioner failing and the chain could potentially last 1000s of miles with proper maintenance before i need to replace it.

 

[m80]

I'm not sure of this theory but,
The crankshaft and camshaft have synchronisation, this being beyond the timing of them at set up.
I would have thought Star / DAS can see this and flag up it it is out of spec compared to the static set up timing marks, or indeed if wear is causing any out of sync at all??
If out of spec there might well be a dash warning and historic code anyway.

I'm sure others can confirm or tell me I'm cocking my leg on the wrong pylon.

 

[Funkyboy]

Bit weird it didn't do it till you added the the other stuff may have blocked an oil feed or as you said thinned the oil too much. Why not change the oil first and see if this cures it now the oil will be back to spec. Buy the oil from mercedes Newcastle on their eBay shop it's £40 delivered. Get your self a £10 electric oil extraction pump. The oil filter is also on top of engine so easy to change. I'd try this first and if the noise hasn't gone after a few cold starts then look to what you were originally thinking.

 

[Notamech]

Bit weird it didn't do it till you added the the other stuff may have blocked an oil feed or as you said thinned the oil too much. Why not change the oil first and see if this cures it now the oil will be back to spec. Buy the oil from mercedes Newcastle on their eBay shop it's £40 delivered. Get your self a £10 electric oil extraction pump. The oil filter is also on top of engine so easy to change. I'd try this first and if the noise hasn't gone after a few cold starts then look to what you were originally thinking.

Did exactly this over the weekend bought castrol edge 229.51 spec oil a jerry can for old oil, a mann filter, a filter socket and a pump on amazon and did an oil change. Will try not using the car for a week and see if the problem persists. The oil that came out did seem thinner than the one that went in. Not sure if its because of the additive or just age of the oil. A month or so ago I did lose some oil as i had a intercooler hose split but after adding the additive the oil level seemed fine so didn't think too much of it. But it does sound like it could have thinned out the oil. Btw what so you guys do with old oil, do local garages take it for a recycling fee? Or do you need to go to the council recycling centre?

 

[Notamech]

So just an update on this everyone. Im glad to say that so far it seems like the oil change has indeed fixed the problem. I let the car sit for a week, started it today and there was no chain rattle. So not sure if it was the additive or a combination of various factors but i would definitely steer clear of any engine oil additives henceforth and stick with using high quality oil instead. Hopefully the 1000 miles that i drove it with the additive didn't cause any damage

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However, I am tempted to get the tensioner changed anyway in case it has started to go bad but am in 2 minds. Would anyone happen to know how these tensioners work? For example are there springs in them that could go weak over time or is it completely oil pressure based? If so there may not be any benefit to changing it. What do you guys think?

 

[m80]

Ignoring the cam hold procedure,
if changing is a simple out with old, in with new I would be very tempted.

 

[colinallcars]

So just an update on this everyone. Im glad to say that so far it seems like the oil change has indeed fixed the problem. I let the car sit for a week, started it today and there was no chain rattle. So not sure if it was the additive or a combination of various factors but i would definitely steer clear of any engine oil additives henceforth and stick with using high quality oil instead. Hopefully the 1000 miles that i drove it with the additive didn't cause any damage

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However, I am tempted to get the tensioner changed anyway in case it has started to go bad but am in 2 minds. Would anyone happen to know how these tensioners work? For example are there springs in them that could go weak over time or is it completely oil pressure based? If so there may not be any benefit to changing it. What do you guys think?

If you’ve established it ain’t broke, don’t fix it.

 

[Notamech]

If you’ve established it ain’t broke, don’t fix it.

Yes you are right. I have finally decided not to unless it becomes a problem where i notice it frequently. Im sure something else like motor mounts etc. will fail on these sooner or later and the money can go towards that.

 

[Tonygw]

I would just monitor it for now, every now and again on cold start, just listen for any tell tail signs, you WILL hear them if its a problem. chances are there is no issue.

Lots of things can fail, but I wouldnt worry until something does, otherwise you could be pumping money into a car with no problems. I learnt this the hard way over the years.

Pretty tough motors these OM651's Plenty about with >200K miles on them. Enjoy

 

[Notamech]

I would just monitor it for now, every now and again on cold start, just listen for any tell tail signs, you WILL hear them if its a problem. chances are there is no issue.

Lots of things can fail, but I wouldnt worry until something does, otherwise you could be pumping money into a car with no problems. I learnt this the hard way over the years.

Pretty tough motors these OM651's Plenty about with >200K miles on them. Enjoy

Yeah i agree... I tend to love my cars and can at times go overboard with the pampering and trying to make it perfect. The reality is its a nearly 10 year old car and it isnt going to be perfect and I need to accept it.

 

[Jonesy161]

As I sit here playing with my old tensioner, cos England have just been stuffed by South Africa and I’ve nothing else to do!!
I can tell you there is quite a strong spring in there, however when I shake the unit I can hear a rattle, I’m tempted to cut the thing in half to investigate.
Glad yours seems ok now, oil change didn’t work for me.

 

[Notamech]

As I sit here playing with my old tensioner, cos England have just been stuffed by South Africa and I’ve nothing else to do!!
I can tell you there is quite a strong spring in there, however when I shake the unit I can hear a rattle, I’m tempted to cut the thing in half to investigate.
Glad yours seems ok now, oil change didn’t work for me.

Yeah I imagine it has a spring and probably a valve of some sort to hold the oil in. Not sure what is the failure point on these though probably that the valves don't function as intended due to crud build up. I know there were a few updates to the tensioners the earlier ones had 2 small oil holes and the newer ones 4 large holes. Not sure which one is on my car but given that its a 2013 facelift w212 im hoping its the newer one and that these fail less. Lets see how things go. if the issue rears its head again i will change the tensioner else it seems fine for now.

 

[kingkhan]

the chain tensioner is easy to replace and costs £45 for an INA brand one which is OE quality
prime the tension in fresh oil before fitting it - A6510500800 this is the part number
fitting takes about 30minutes- just make sure the engine is at TDC otherwise takes some brute force to push it in =)