Timing Chain Question

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davinci

New Member
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Jul 18, 2007
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19
When should the timing chain be checked? My e200 komp has covered 125,000 miles and is due a b service in about another 5,000. Is it checked then or shouild I ask to have it checked asap???
many thanks
 
Its something that you cant check very easily, if its quiet on start up and there is no rattle, there is no other way of telling.
 
my uderstanding is that you can check for "chain stretch"/wear.

You would normally be able to put a strobe onto the timing wheel markings at fast idle and see the advancement/retardation.

If it is several degrees from spec then the chain has more stretch/wear in the links than it should, and needs changing.
 
my uderstanding is that you can check for "chain stretch"/wear.

You would normally be able to put a strobe onto the timing wheel markings at fast idle and see the advancement/retardation.

If it is several degrees from spec then the chain has more stretch/wear in the links than it should, and needs changing.

Allowing for any errors, then it would be better to slip the cover off and put it on TDC and see if the timing marks line up
 
my uderstanding is that you can check for "chain stretch"/wear.

You would normally be able to put a strobe onto the timing wheel markings at fast idle and see the advancement/retardation.

If it is several degrees from spec then the chain has more stretch/wear in the links than it should, and needs changing.
If the tensioner is working properly, how can putting a strobe light on show you if the chain is worn ?
 
If the tensioner is working properly, how can putting a strobe light on show you if the chain is worn ?

It cant really as there are other equations. Only by taking off the cover and setting it to the timing marks can any wear be seen.

The tensioner has nothing to do with the effect that any wear would have, as it only takes up the slack and that has nothing to do with the timing.
 
It cant really as there are other equations. Only by taking off the cover and setting it to the timing marks can any wear be seen.

The tensioner has nothing to do with the effect that any wear would have, as it only takes up the slack and that has nothing to do with the timing.

I could be pedantic and point out that stretch is one of the effects of wear?

Or have I just made a fool of myself? :eek:
 
I could be pedantic and point out that stretch is one of the effects of wear?

Or have I just made a fool of myself? :eek:

No you are correct, the tensioner masks the outward signs of wear, including most of the noise that is only there on start up. The 113 engine has some very clever design points in the the crankshaft balancer rotates when you stop the engine leaving it in a retarded state. There is a one way ball valve in the tensioner oil feed that keeps the slack in the chain under tension, so just listening on start up is not a good test. With variable camshafts the Strobe will not tell you much about the wear that has taken place.
Other engines may use the same techniques, I do not know as I have not studied them.
The word stretched does not mean that the links have stretched, though they could it is more the wear that takes place in th moving joints, what do we have there,say 90 links. Multiply that out say with just a few microns on each and you could measure several mm of stretch
 
I could be pedantic and point out that stretch is one of the effects of wear?

Or have I just made a fool of myself? :eek:

There was a post on this some time back - interesting to note that chains don't stretch.... - sure , they wear , but they don't stretch.

In general the sprockets will "hide" more wear than the chain itself .
 
There was a post on this some time back - interesting to note that chains don't stretch.... - sure , they wear , but they don't stretch.

In general the sprockets will "hide" more wear than the chain itself .
The chain does not really "stretch" in terms of the metal stretching as such, it becomes longer due to the chain link pins wearing, thus making the chain longer (MMs) and free play with wear in the sprokets and the parts of the chain that sit in the sprockets.

The only true way of telling if a timing chain has worn considerably is to remove it and inspect it. (On some larger engines a dial test indicator is used to check the chain run out with the tensioner disengaged)
 
I forgot to say that when the balancer on the crankshaft rotates as the engine stops to put it into the retarded mode, it blanks off the oil drain from the main bearing gallery keeping the oil within the bearings.


fredfloggle brought up the sprockets, a good point, as when they wear it is possible for the chain to jump or override the sprocket.

If you check for wear in the system by taking off the cover, then if the sprockets have sharp pointed teeth, then they should be changed. In practice the teeth come though the chain when sitting on the sprocket.
 
Always change sprockets with chain - unless the sprockets have done extremely low mileage.
 
The chain does not really "stretch" in terms of the metal stretching as such, it becomes longer due to the chain link pins wearing, thus making the chain longer (MMs) and free play with wear in the sprokets and the parts of the chain that sit in the sprockets.

The only true way of telling if a timing chain has worn considerably is to remove it and inspect it. (On some larger engines a dial test indicator is used to check the chain run out with the tensioner disengaged)

Again - Quite right . The old way is to hold the chain like a snake and assess the lateral play which is proportional to pin and fishplate wear.
 
The whole point here is that if you took the chain off to test it after 125k miles, no one would put it back again, you would replace it along with the sprockets, also checking the condition of the guide rails. The labour far out ways the component cost
 
Agree entirely. If I was doing this on mine at this mileage, I would be tempted to change a lot more items while the chain was off, but then that's a personally view.
 

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