SL560 M117 – Timing chain, guides, and tensioner at 100K?

[yjmeian]

My SL560 (M117) just hit 100K miles. Runs perfectly, no noise or issues. Timing chain, guides, and tensioner have never been changed. Do I really need to replace them now, or can I wait until there are symptoms? Has anyone drove more than 100K with no issues?
Thanks

[engatwork]

You should be ok for at least another 50k miles. I'm assuming you do regular oil changes.

[porkface]

we always pulled valve covers at 100k during oil changes to check chain stretch. they can fail before 100k but usually by 110k or 120k, the chain has stretched enough to dictate replacement. the sl means you have to catch this BEFORE any thing goes bad. oil pan might have to come off and you really want to avoid this.

pull both valve covers and look at the plastic chain guides. the inner 1 on the lh head is the most fragile of the bunch. because of the way the chain runs, it's the 1st to break. any broken bits must be fished out of the engine. pull the lower oil pan and get the pieces-which isn't there on the sl. you have to pull the pan to fetch the broken bits. they can get into the oil pump from there or the new chain can jump if a piece falls out of the timing cover. seen it twice.

while the covers are off, turn the engine by hand clockwise to tdc on the crank pulley. there are marks on the cams and heads to line up. keep turning the motor until the marks on the lh cam line up. then, look at the crank pulley. if the pulley is PAST tdc 6 degrees or more, you need a chain and tensioner. at 4-5 degrees, seriously consider replacement because of the oil pan.

good luck, chuck.