When is it time For a new Chain?

[500eguy]

Ok guys, what are the usual signs telling you need a new Timing Chain? Is it going to Rattle all the time at the front? will it rattle When cold only?  Does it run rough? just curious because the majority of my Mercs have the m117, none of the cars are acting strange... just curious just to be sure.

[Andrew280SEL]

Good topic Johnny.

I'd like to know this also.

[500eguy]

I dread the day i am driving down the road and my car just stops and does not want to start again. It happened once in my 450, they said when they took the valve covers off my old seized motor it was full of old sludge gunk because the previous owner never changed the oil often. So i would hate to have the chain screw up!

[Des]

Timing chains should be replaced every 5 years, with all the rails, glides and tensioner.

My 230 only rattles the timing chain when cold.....rattle rattle rattle, after about 5 minutes it is fine, although fuel consumption is also poor and going up hills it starts to rattle again.

Driving a V8 W116 I would have it replaced if unknown the last time it was done, far better to do it than have your motor turned into a heap of worthless metal.

[Big_Richard]

Timing chains should be replaced when their stretch limit has been reached, Or at a given milage, which will be documented in a cars service manual. There is no magic number applying for all cars as to when to change it.

[CraigS]

I put in an earlier post regarding this that if you don't know when the timing chain was changed - if at all, then it should be done, subject to the method outlined by Styria. The chain tensioner should also be changed at the same time, as well as the top chain guides. In the long term, it is cheap insurance, and if only for the peace of mind.

[500eguy]

thanks guys, i will be looking into this with my SEC, i think during the Engine swap my chain was replaced... not to sure.

[WGB]

Chain stretch on an M117 is 11 degrees max using the method prescribed by Styria earlier in the post.

It is a combination of actual chain stretch as well as wear on the sprockets and the surface of the chain.

The plastic "sliders" start as a milky white and gradually darken to a dark "Mahogany" brown. If they are brown they need to be replaced as they become brittle and will break up and cause the chain to jump.

The real villain is the hydraulic chain tensioner which in the 117 motor has no ratcheting mechanism (unlike the m100) and when it is worn exerts little pressure on the chain until the oil pressure is restored after startup. The chain can thrash around for a few seconds and that is when the tensioner slipper and plastic sliders can break up and the chain can jump.

Recommendation is new chain every 100,000 km (60,000 miles) with a new tensioner and examine the rest at the same time.

You will not get rid of all the measured stretch by changing the chain alone as the sprocket wear will also cause a change in timing.

Bill

[Andrew280SEL]

Does the M116 motor suffer the EXACT same problem?

I mean, I know it also suffers possible engine destruction but is it exactly the same as the M117?

[WGB]

I thought that the M110 motor didn't jump chains - they just got noisier and noisier but I was at  a wreckers a few weeks ago and the young guy was telling me about a 116 - 280 that he bought off the boss for $400.

He took it for a run in the country and apparently the chain let go and trashed the motor at speed so I guess they do have problems of some sort.

Bill

[Andrew280SEL]

I was talking about the M116 motor in the 350's.

[WGB]

Sorry Andrew the 280 in your monniker threw me off - As far as I know the M116-3.5 motor has all the same potential problems with it's timing chain as the M117-4.5 and this continues into the 126 series with the alloy block - M116-3.8/4.2 and M117-5.0/5.6.

There was a small series of motors in the early 1980's 126's which used only a single row chain and not the normal double row. I don't know what the reason was  - either fuel efficiency via friction reduction  (There were a lot of changes to the 380 and 500 models in the second year of production (I think - 1981 or 1982) to make them more economical, including a change to taller diff ratios) or economy of manufacture (unlikely). These chains stretched in the first 20,000km and presumably all were converted back to double row chains and sprockets under warranty.

I remember seeing one being converted in Franks Auto Services in the early 1980's in Dunedin, New Zealand and Frank showed me the single row chain that he had removed with suitable disparaging comments being made. That was the first time I looked and marvelled at how long the chain really is in a Mercedes V8 Motor.

Bill

[Andrew280SEL]

Thanks Bill, I'll be extra vigilant with the 350 in that case.

[WGB]

Obviously the chain and it's stretch is important as is the brittleness of the plastic sliders but the real culprit I believe is the timing tensioner which gets sloppy and does not hold it's tension at startup or with low oil pressure.

Bill

[CraigS]

Or seizes completely, as was the case on my less than 200,000 km 6.9.