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that is interesting
i have a 2008 full-size supercharged with 232K mi
i did the full chain/tensioner/guide install about 2K mi ago

motor had a nasty rattle at start up for about last 50K mi
now after replacement its quiet

worth it to me because got so many strange looks and comments when started the car before and just didn't sound like was prolonging life of anything mechanical

thanks for posting
 

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very interesting... so if I'm reading that right the root of the issue isn't so much with the guides/chain as everyone assumes, but with this hydraulic tensioner that fails leaving the chain slack @ temp causing the actual damage?
 

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It's my understanding that the tensioner as originally designed is a) harder than the guide b) at an incorrect angle to the guide surface upon which it pushes. So over time, under circumstances which are not 100% clear to me (i.e. All engines? S/Cs? Driving habits? Oil changes?), the tensioner wears a recess into the aluminium guide rail. If this recess gets deep enough, the tensioner becomes stuck in the worn recess and the guide is no longer serving its purpose of keeping the chain tight because the tensioner and guide are jammed together - not moving anymore. The revised design a) put a steel pad on the guide rail and b) changed the tensioner angle. To my understanding this is why you have to change the guide and the tensioner.
 

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that is interesting
i have a 2008 full-size supercharged with 232K mi
i did the full chain/tensioner/guide install about 2K mi ago

motor had a nasty rattle at start up for about last 50K mi
now after replacement its quiet

worth it to me because got so many strange looks and comments when started the car before and just didn't sound like was prolonging life of anything mechanical

thanks for posting
I don't think this is an issue on the 4.2.
 

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Just got a 2008 sc and no noticeable noise on start up with temps at 50F. Today in lower 40's there is a 2 second rattle on start up and after a few hours of sitting a 1 second rattle. I really thought I was avoiding the issue with the 4.2 but am now wondering what that rattle might be. Supercharger coupling or something else. Engine seems quiet while running when up to temp. At 128,000 miles.
 

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very interesting... so if I'm reading that right the root of the issue isn't so much with the guides/chain as everyone assumes, but with this hydraulic tensioner that fails leaving the chain slack @ temp causing the actual damage?
Interesting. The BMW M62tu's had a similar issue with their stock tensioner design, hence the updated tensioner with a longer, stiffer spring to keep more tension on the chain at all times, even with low oil pressure on startup.
 
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