Timing chain, good advice or bad? - Page 3 - PeachParts Mercedes-Benz Forum

Simpler=Better · #31 11-02-2015, 09:40 AM

Easy guys, jeez. Who knows maybe the PO threw a new chain on at 100k.

Pop the valve cover off, take a look at the rails-if there are grooves okay they need replaced. Might as well throw a new chain/tensioner spring/rails at it while she's open. Build/buy the 6mmx1.0mm pin puller.

It's not terribly complicated, just take your time and double check everything as you go.

If you drop the chain or turn the engine over don't panic, these are easy enough to re-align with a dial indicator & some brains.

babymog · #32 11-02-2015, 09:52 AM

Hate to offend any who haven't already been offended, ...

I would not trust that a new chain has the exact same length as the original, if you're going to that much trouble just time the thing. Add to that the potential for 1 or 2 degrees of sprocket wear, worth the trouble.

Replacing the cam gear at least will help future chain wear, somewhat, but since the crank gear gets twice the rotations and the combined torque of the camshaft and IP and vacuum pump, ... it is the highest wear. The teeth wear, and this affects timing. When the chain wears you have a chain with a distance between links that is greater than the distance between sprocket teeth, so only the last tooth engaged is pulling the chain, which increases the rate of wear greatly.

Second, I do not feel that I would wait for noise from the chain to indicate failure. I have not had a chain fail, maybe someone here has and can tell us what sound it makes prior to failure and how much warning is given by this sound, ... but it seems like a long-shot.

leathermang · #33 11-02-2015, 09:55 AM

Quote:

Originally Posted by Stretch

.....For example: If you'd (politely) told the atypicalguy guy that chain elongation is expected in an OM617 motor this thread probably wouldn't be as long.

Atypicalguy appears to be over forty years old. He has some mechanic who did not blink when he told him he had NO stretch at close to 200,000 miles.

My first post was clear and short. His measurement was not correct.
He did not want to accept my pronouncement of what to anyone else is obvious.
When I tried to lead him to thinking about his situation he refused and declared my question pedantic. It was in the spirit of Socratic Method.. so by definition pedantic.... I accept that as accurate description.

Socratic Teaching

Now , to the idea that YOU would be worrying about how long a thread is... you made my morning....

Stretch · #34 11-02-2015, 10:18 AM

Quote:

Originally Posted by leathermang

Atypicalguy appears to be over forty years old. He has some mechanic who did not blink when he told him he had NO stretch at close to 200,000 miles.

My first post was clear and short. His measurement was not correct.
He did not want to accept my pronouncement of what to anyone else is obvious.
When I tried to lead him to thinking about his situation he refused and declared my question pedantic. It was in the spirit of Socratic Method.. so by definition pedantic.... I accept that as accurate description.

Socratic Teaching

Now , to the idea that YOU would be worrying about how long a thread is... you made my morning....

Further justification wasn't necessary.

I was hoping that you would take my post as constructive criticism and perhaps try to stop giving people a hard time as well as "good" advice.

Never mind.

t walgamuth · #35 11-02-2015, 10:31 AM

I've had a lot of these engines over 200K and have never changed a timing chain unless the engine was apart for an overhaul or major repair.

I understand the concept of zero wear being impossible, but do support the idea of insignificant wear, unmeasurable wear or measureable but manageable wear. I am also pretty sure we've never replaced any sprockets when going through these motors and have not had any bad luck with them so far.

I am not certain how possible it would be to replace guides without losing the timing as some are pretty deep into the motor.

Of course all bets are off if the engine is not taken care of with regular oil and filter changes or using the wrong oil.

atypicalguy · #36 11-02-2015, 10:33 AM

Sorry; didn't mean to poke the bear.

Thanks to everyone who actually contributed to this thread.

Sent from my SAMSUNG-SM-N910A using Tapatalk

leathermang · #37 11-02-2015, 10:50 AM

Quote:

Originally Posted by atypicalguy

Sorry; didn't mean to poke the bear.

Thanks to everyone who actually contributed to this thread.....

The Bear wants to know if you now understand that it is not possible that at that mileage there is NO wear ? That either you measured wrong... or some intervening variable exists ? Like a PO who over-corrected with an offset key on the cam sprocket ?
and ... it was not YOUR thread in the first place....

babymog · #38 11-02-2015, 10:54 AM

Quote:

Originally Posted by atypicalguy

Sorry; didn't mean to poke the bear.

Thanks to everyone who actually contributed to this thread.

Sent from my SAMSUNG-SM-N910A using Tapatalk

A passive-aggressive posting, implication that certain posters did not contribute, is "poking the bear" and usually gets the expected response.

If you truly are here to get a useful answer, which occurred many postings ago, and not troll, this would not be happening.

None of us are perfect, but sometimes the underlying hostility is well fed.

leathermang · #39 11-02-2015, 11:01 AM

Jeff, He may not have been wanting a useful answer....as his first post did NOT pose any question.... he made a statement which defied physics.... and I responded to that.

atypicalguy · #40 11-02-2015, 11:42 AM

Yes trolling often begets trolling. Sorry for my part; when you are being simultaneously patronized and provoked the temptation occasionally prevails.

Any number of posters have contributed meaningfully here, describing methods of timing chain stretch measurement with which I was unfamiliar etc. I am not sure the original poster's question was answered conclusively however. My contribution was to share my own direct experience with the matter at hand, nothing more or less. I do feel it is relevant, as people reading this are more likely to be people like me than they are to be experts.

I did learn in this thread about tooth loading with chain stretch, which I had not considered despite many years of bicycle riding.

It is also interesting to hear opinions, e.g. Manny's philosophy on general principles. In my own case I will only offer that I considered rolling it in, but did not have the time or tools or an extra set of hands to help me with the new chain. So I measured it as best I knew how, asked the best mechanic I know, and took his advice. I said it the way I said it for a reason: the mark was perfectly aligned as best I could tell despite expecting to find some stretch, knowing about anticipated wear-in, etc. This should be relevant to anyone trying the job for the first time in their driveway, as I was.

I'm sure this will all be used as ammunition by Leatherman to lecture me on my inexperience, ineptitude, errors, need to perform completely irrelevant calculations, or what have you. I If the conclusion of a reasonable person reading this thread is that measuring stretch is best left to others, then fine. But the fact remains that at least two people here have looked at it and found it to be negligible on high mile motors. Leatherman cannot prove over the Internet that it was done incorrectly in my case; he will have to come over and measure it himself, which he is welcome to do incidentally. Until then I would suggest that he employ more circumspection in his comments, if the true intent is to influence thinking, and not score anonymous Socratic internet method points. But I'm sure he or she is smart enough to figure that out without my assistance =:-)

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ah-kay · #41 11-02-2015, 11:48 AM

Quote:

Originally Posted by atypicalguy

Yes trolling often begets trolling. Sorry for my part; when you are being simultaneously patronized and provoked the temptation occasionally prevails.

Any number of posters have contributed meaningfully here, describing methods of timing chain stretch measurement with which I was unfamiliar etc. I am not sure the original poster's question was answered conclusively however. My contribution was to share my own direct experience with the matter at hand, nothing more or less. I do feel it is relevant, as people reading this are more likely to be people like me than they are to be experts.

I did learn in this thread about tooth loading with chain stretch, which I had not considered despite many years of bicycle riding.

It is also interesting to hear opinions, e.g. Manny's philosophy on general principles. In my own case I will only offer that I considered rolling it in, but did not have the time or tools or an extra set of hands to help me with the new chain. So I measured it as best I knew how, asked the best mechanic I know, and took his advice. I said it the way I said it for a reason: the mark was perfectly aligned as best I could tell despite expecting to find some stretch, knowing about anticipated wear-in, etc. This should be relevant to anyone trying the job for the first time in their driveway, as I was.

I'm sure this will all be used as ammunition by Leatherman to lecture me on my inexperience, ineptitude, errors, need to perform completely irrelevant calculations, or what have you. I If the conclusion of a reasonable person reading this thread is that measuring stretch is best left to others, then fine. But the fact remains that at least two people here have looked at it and found it to be negligible on high mile motors. Leatherman cannot prove over the Internet that it was done incorrectly in my case; he will have to come over and measure it himself, which he is welcome to do incidentally. Until then I would suggest that he employ more circumspection in his comments, if the true intent is to influence thinking, and not score anonymous Socratic internet method points. But I'm sure he or she is smart enough to figure that out without my assistance =:-)

Sent from my SAMSUNG-SM-N910A using Tapatalk

Well said. x 2

leathermang · #42 11-02-2015, 11:54 AM

Quote:

Originally Posted by atypicalguy

.... My contribution was to share my own direct experience with the matter at hand, .....

Which left the possibility of misleading others less experienced with machines...
That is why it needed to be addressed.

atypicalguy · #43 11-02-2015, 11:58 AM

Despite all the knowledge shared, I am not sure whether I am any less confident in having not replaced it frankly, and that decision is really what the thread is about.

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Diesel911 · #44 11-02-2015, 12:52 PM

Quote:

Originally Posted by shertex

FWIW I've had two very experienced MB mechanics tell me the same thing....that you will hear something prior to catastrophic failure. I was concerned about this on my 92, which I sold with 263k miles on the clock. In the case of the 91, well maintained and 116k miles, I of course have no concerns.

There has to be a reason for the failures.

There is a thread somewhere that has that I think it was there was some timing Gears that were too soft to fault heat treating and the advice was to inspect them.

On the 1985 Engines and when I as what causes Timing Chain Failure it turned out to be the Vacuum Pump.
Then I ask what caused Vacuum Pump Failure. Older Vacuum Pumps had Ball Bearings with a Plastic Cage and no shields. The Plastic Cage eventually feel apart and the Balls came out of them.

But what can kill all of them is when the Timer Bushing gets too much end play.
One of our Members killed 2 Vacuum Pumps due to that Bushing.

The parts from the rear of the Vacuum Pump fall into the Timing Gear and Chain.

The new Engines have the Timer Gear attached to the Fuel Injection Pump Cam shaft so there is no Bushing to wear but they can still have Vacuum Pump Failures.

jabstick420 · #45 11-02-2015, 01:06 PM

I am in the same boat... with 190K on my 83 300cd turbo.

using the 2mm lift I measured approx. 3 degrees of stretch.

most diy posts describe rolling in new chain and installing new tensioner.

the lower rails seems like a pain to get to.

would it be prudent to change out the chain, tensioner, tensioning rail and upper slide rail?

that would leave out the two lower rails, and sprockets unchanged. assuming the sprockets don't show severe wear.

not sure if there is a way to inspect the lower rails for wear...

any input would be appreciated