> Skipping timing chains is a very very rare phenomena,
> but something that I think gets accused of happening
> a fair bit.
I am not qualified to judge the general rarity of timing chain slippage
( or, I suppose, jumpage ), however, I have a Mercedes 300SD (
turbodiesel motor with a hydraulic timing chain tensioner ), and I have
watched the timing chain whip around madly after the tensioner piston
has failed. The chain develops erratic moving waves, with an amplitude
of perhaps a half inch at 1500 rpm or so. Given the right wave pattern,
the chain could develop a hump right before pickup by the cam sprocket,
effectively removing one or more links from the chain, so that the chain
moves forward by the same number of links. I have watched this only at
idle to 1500 rpm, for fear of just this sort of thing happening: the
oscillations increase dramatically as engine speed increases. A
Mercedes technician I spoke with confirmed that a failed timing chain
tensioner can lead to a skipped tooth, which can lead to impassioned
wailing, at the very least.
-Stuart Steele
1969 TR6
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