I've been thinking about this a lot lately. I've seen pictures of engines after the chain snapped, and really caused some damage. If I'm at 167K now, about how long should I wait to do the timing chain?

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1985 300D
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1970 Jaguar E-Type OTS
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2011 Ford Crown Victoria

There is no time. When the chain passes 8 degrees elongation its time to consider it. Keys are available to correct up to 10 degrees.

Use synthetic oil and you may never need to change it.

Meaning your engine will be so well lubricated the chain will hardly stretch?

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1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Yes. Synthetics are light-years ahead of dino oils.

keep this in mind when trying to understand this effect.
the chain does not stretch.
the gears and links wear. quality oil and proper filtration/changes prevent wear.

I don't want to appear to be too stubborn - but - my experience with bicycle chains is that they do stretch as well as wear into the sprockets. Most of the time I see that the chain links are more worn than the surface of the sprockets but I think the death of a bicycle chain (at least) is that the links get bent / stretched out of shape. I'm just transferring my bicycle experience to an OM617! (Heaven help us)

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1992 W201 190E 1.8 171,000 km - Daily driver
1981 W123 300D ~ 100,000 miles / 160,000 km - project car stripped to the bone
1965 Land Rover Series 2a Station Wagon CIS recovery therapy!
1961 Volvo PV544 Bare metal rat rod-ish thing

I'm here to chat about cars and to help others - I'm not here "to always be right" like an internet warrior



Don't leave that there - I'll take it to bits!

Bicycle chains are not quite like timing chains. A bike chain has to have some side play for it to change sprockets and move with that nonlinear working line.

Not quite... the number of teeth (drive ratio) doesn't change but the total length does.

I just did mine with the same mileage, plus the banana rail.

What is the banana rail? Am I going to be slapping myself in the forehead for not knowing what it is?

__________________
Never be ashamed to ask for help.

1985 300D
1987 300SDL
1970 Jaguar E-Type OTS
2002 Dodge Intrepid (Traded In)
2011 Ford Crown Victoria

On our '95 E300 I changed all the tensioners, slides and guides when I did the head gasket at ~260k miles. I did not change the chain at that time realizing that I'd be able to come back and roll a new one in eventually. I was going to try to get at least 300k out of it before installing a new one. The car has had a very aggressive service schedule.

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Jim

It's the largest slide rail on the passenger side of the car next to the tensioner. It's shaped like a banana and when it wears it has grooves in it.

ha! yeah, I'm sure it is the case with bike chains. but the MB chain literature I've read states plainly that "stretch" is a misnomer. the length of the chain is unchainged...(sorry for the pun) it's all in the wear of the contact parts.

actually, now that I think on it... I'll bet the bike chains remain the same length also... the outer links would have to actually stretch to increase the length of the chain. what's gotta be happening is the rollers ride on the pins, and the wear on the inside of the rollers, and the pins, and the teeth of the gears all wear. the overall length of the chain itself remains unchanged.

no?

The chain does not stretch (bicycle or timing), but it does change length. As the pins and holes wear, there is more clearance and thus the chain becomes longer.

On a bicycle, like a timing chain, when you can lift the chain in the middle of the sprocket/gear with it being tight on both ends, the chain is "stretched" and should be replaced. When the chain becomes longer or "stretched" if you prefer, you have two problems: One is the timing change (retarded valve and injection timing), the other is that the chain now pulls on only the last tooth of the sprocket/gear, causing more stress & wear to the teeth. A proper chain will distribute the wear better and the gears last longer.

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MB only says "excessively elongated", but I have never seen an official description as to what "excessive" actually is.

They provide keys up to 10*, but I'd be hesitant to use something that large. I've only used the 4* keys in both my cars.

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More data on this topic..

Timing chain stretch does not exist
Timing Chains Don't Last Forever






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