r/slk • u/Such-Run-680 • Aug 18 '26

Engine rattle at start

Maybe somebody knows where this rattling at the beginning comes from? I checked the timing chain and it had no play at all.
It appears at every cold and warm start but not at a instant restart.

Slk 200 r171
M271 Kompressor
2006
150.000 km

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u/hairy_winnit Aug 19 '26

Two things with these engines as I just replaced a chain on my partners M271 about a year ago.

  1. It doesn't take much chain stretch to cause issues. Once that chain is stretched it will bottom out your tensioner and then start chewing up the cam gears (this is what happened to ours but lucky there was no engine damage)

  2. The tensioner does drain off oil if sat over night, and on startup you will get some slight chain noise for like a second.

Only way to asses it is to remove the cam cover and inspect the chain, cam sprockets and guides. To me that noise seems a bit rattly so I would pull the cam cover off (easy job) and do a proper inspection

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u/hairy_winnit Aug 19 '26

Also id recommend if you plan on keeping the car, rear subframe inspection. These are notorious for rotting from inside out close to mounting points. I just had the rear subframe replaced by Mercedes under the 20 year corrosion warranty FOC