Anyone experience a timing chain failure?

[need2speed]

Just wondering if anyone has experienced the dreaded happening, or has first-hand knowledge of someone who has. What mileage and type of use? Mine is up for scheduled replacement in a few thousand K's but I will be travelling with the car extensively over the summer and would like to know if it can wait. Very spendy

 

[gsxr]

Dean,

I have never heard of an M119 chain failing. I recall hearing of one case where the chain guide rails failed and caused the engine to lock up, but I think that was while cranking/starting, not while running.

You can approximately determine chain health by measuring the stretch; this requires pulling the passenger valve cover and fan clutch. You slowly turn the engine by hand (via the crank bolt) until you can pin the right exhaust cam with the factory tool. Then read the degrees on the balancer and subtract from 45. Repeat several times to ensure an accurate measurement. For example, if it shows 41° on the balancer, that is 4° of chain stretch. There is no factory spec published for the M119, but based on specs for other MB engines, I would get nervous if the stretch is 6° or more. About 4° or less is nothing to worry about. MB tends to indicate that 2° (approx) is considered normal after a break-in period of 10-20kmi. A brand new chain & guides will read 45° (zero stretch) via the method above.

Side note - rolling in a new chain is not that expensive, maybe 2-4 hours labor and <$200 in parts. However, replacing the guide rails is $$$$ due to the amount of stuff that has to be removed. The rails are usually due for replacement by 150kmi, sometimes sooner... the spare '92 motor I picked up a few years ago had ~70kmi but the upper rails were broken. The upper rails can be inspected visually by removing both valve covers.

 

[2phast]

You should also pay attention to the noise your engine makes when it initially starts up after a oil change. If you hear a clunking (rattling?) its a good indicator its time to change your chain. Failure normally occurs during this startup period.

As for parts cost, its a bit more than $200. This is my parts list which I received at Mercedes Employee cost.

Gasket set - $23.65
Gasket kit - $24.20
Roller chain - $184.80
Chain tightener - $155.10
Ring seals - 11.88

I paid tax as well, total was $437.59.

Changed my chain at 165k, but it had been making noise for at least three oil changes. Was pushing my luck for at least 12k miles. Not a good idea!

 

[gerryvz]

I too have never heard of an outright chain failure. It doesn't seem to be an issue with the M119, rather more of a "proactive" maintenance item. I would think that a well-kept engine could go 125-150K before requiring a change of chain. And would in general recommend a guide rail change at the same time a chain changeover is done.

Generally the danger period on chains is upon cold start. I don't have direct experience with the M119, but the timing chain is definitely a weak spot / something to watch with the predecessor M117 engine, which is notorious for chain/guide wear and failure. The M117 has, upon cold startup, what is called a "death rattle" which is an audible noise. When you hear this, your chain/guides are on borrowed time and the chain must be replaced immediately. Wear and mileage is NOT necessarily the primary cause of chain stretch: my 1987 560SL had the death rattle after only 45K miles on it!! Age and non-use can be just as deadly for a timing chain as mistreatment. I don't know how this is with the M119 as I don't (yet) have the experience, but I believe chains in general, though more reliable with the M119, should be proactively changed by 150K miles at the outside.

Cheers,
Gerry

 

[gerryvz]

You should also pay attention to the noise your engine makes when it initially starts up after a oil change. If you hear a clunking (rattling?) its a good indicator its time to change your chain. Failure normally occurs during this startup period.

LOL you posted right before I did, and I was saying the same thing exactly without seeing your post !!

 

[2phast]

LOL you posted right before I did, and I was saying the same thing exactly without seeing your post !!

Haha, yea just noticed that as I was editing my post to included the required parts necessary for a chain replacement.

 

[need2speed]

Great to hear...thanks all! I don't have any noises but will check for stretch.

 

[omegabenz]

no, but if you jump a tooth (or teeth: yikes), you could slap the valves. Id take off the valve covers and inspect. You could always replace the guides you can get to and roll in a new chain for now. A full timing chain with changing all the rails including the ones in the timing cover is really a winter job! If you plan on high speed/acceleration driving this summer, you may want to just do it now to alleviate any anxiety regarding chain slip. If you are doing time trials, it would probably run better if you do it all now.

 

[Cannoli]

I just had my timing chain replaced this past winter. The right bank intake cam DID jump a tooth. The hydraulic cam advance system wasn't working and had to be serviced. Replaced ALL plastic chain guide bits - boy they were brittle! Replaced the water pump and anything else that was being touched. All told, about $4k. The engine had ~ 160K miles on the clock.

 

[szvook]

I opted to have the chain replaced as a precautionary measure and although I did not hear any noises, when the chain was checked, it had very slight play with 115K on the clock.

I had the following replaced with new, at the tune of $1585.00

Upper Side Rails
Timing Chain
Chain Tensioner
Upper Guide Rails
Valve Cover Gasket
Front Engine Cover Seals
Lifter Tube Seals
Power Steering Fluid
Power Steering Tank Seals
Power Steering Pump Filter
Air Filter mount

I should be good for a while.

 

[gerryvz]

The right bank intake cam DID jump a tooth.

Wow, I didn't know that a chain jumping a tooth wouldn't cause catastrophic damage. On an M117, a one-tooth (18-degree) jump will nearly always bend at least a few valves, requiring the heads to come off and be refurbished or replaced.

You dodged a bullet there, Norm! Good to know about all of the other stuff that you had done. I'm at 112K on my car, so probably looking toward the time where I'll have to do much of what you and svzook did....

Cheers,
Gerry

P.S. Steve ... what are the "upper side rails" you mention as the first item in your list?

 

[szvook]

what are the "upper side rails" you mention as the first item in your list?

Since the cylinder heads have four rails, I was told to replace them all, as all rails get replaced. On my work order receipt, the item is listed as Upper Side Rails, maybe it should have read Top Side Rails. So maybe its the way my service tech lists them.

 

[gerryvz]

Oh, OK - so they are part of the set of upper chain guide rails. Got it. Thx. Terminology just threw me a bit.

 

[szvook]

Oh, OK - so they are part of the set of upper chain guide rails. Got it. Thx. Terminology just threw me a bit.

Yep and you just beat me to the punch.

 

[gsxr]

It's actually a bit more confusing. There are three guide rails pinned inside the cylinder heads... one on the right (passenger) head, and two on the left (driver) head. Then there are the clip-together rails above the cam sprockets. And of course two more down inside the timing cover, which are $$$$ to replace as they require pulling the timing cover, which is $$$$ if I haven't already mentioned that. Fortunately the lower rails have a much lower failure rate, it's the upper rails (inside the heads & above the sprockets) that need attention.

See page 2 of this PDF in the FSM:
http://www.w124-zone.com/downloads/MB%2 ... 5-3330.pdf

The rails above the sprockets are 6 and 16.
The 2 rails in the left head are 14 and 26.
The 1 rail in the right head is 8.
The 2 lower rails inside the timing cover are 3 and 29 ($$$$).

6 & 16 can be replaced by pulling the valve cover.
8, 14, and 26 require pulling the chain tensioner and disassembling BOTH camshaft adjusters (very advanced DIY).

 

[need2speed]

Well, the chain was replaced along with the upper guide rails. The mechanic showed me all the parts and only minimal wear was apparent. I feel better anyway...

 

[szvook]

Well, the chain was replaced along with the upper guide rails. The mechanic showed me all the parts and only minimal wear was apparent. I feel better anyway...

Excellent news