87 560s el 225000 miles, noisy knock om rt side valve train.

Tryed to turn motor by hand after plugs were out but sometimes it would bind. Don't "see' any bent valves (from top side) compression was about 150 on all eight

My conclusion:

Not jumped as timing marks ( both cams) line up with 6-7 dgrees after tdc on crank.

Possibly the lower rail has been destroyed and has become caught in the chain when it binds/locks up.

Should I pull the entire cover or go ahead with the new replacement chain. Also an going to repalce all the rails and tensioner. Which do you replace frist
the rails or the caih!

The chain on the top side passenger side has about 1-1.5 "slack" inche which can be raised very loosely


Any help or ideas appreciated!

Thanks
John

Of course start by removing the oil subpan & see if there is any plastic chain rail debris there.

I always replace the rails first, to make sure they aren't broken & pieces of them are in the front cover or pan.

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Nothing in the sub Plan. Very clean.

The chain is ver very "loose/slack" betweeen the two cams, if that makes sense.

Should just replace other rails first then the chain or vise vs or would you go the length to look at the bottom rail. Keep in mind the timing does not seem that far off?

Thanks so much

John

Anyone??

John

If you're seeing slack in the timing chain, I would really suspect that your timing tensioner has given up.

Admittedly, I haven't worked on the v8 engines much yet, just tearing into one at the moment, but from what I've understood from studying other's comments, the tensioner should maintain some tension even without having pressure.
In my SD, for example, there is a spring inside that keeps it from slapping on starting.

Assuming I read the chain pattern properly, you shouldn't see the slack on the top of the chain when you're pulling the chain around in the proper engine rotation, to check the timing marks. This would be due to the crank pulling everything, the tensioner being on the "outlet" side of the crank sprocket. When it's snug that direction, if you had slack below the right cam, that would seem to point to tensioner, or possibly the rail.


I hope that I'm not barking up a tree here, and that I wrote that somewhat coherently!

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...

Which direction did you turn the engine?

Turning it clockwise, facing the engine!

I can't see how you have slack between the cams if you are turning the engine clockwise.