Dokus

https://youtu.be/-CFiDBFGzko



For a while I been having a new clicking/knocking sound in my cls55 which I'm having problem locating. It's present in the very beginning of the video and trough out. It's that tapping/knocking/clicking sound which differ from the normal nosies.

It's very load in person and you can hear it well inside the car.
It's only present at cold start and not every cold start so it's seems random.

At first I thought it was the belt tensioner but the sound does not seem to come from that area.

Any ideas?

SICAMG

I believe It's coming from the supercharger pulley backing plate. There is a high spot somewhere on the plate and will make that random sound and also change cold to hot.

Dokus

Could be a possibility. I will keep investigation going. Should I do anything about it if it's the pulley or is it just the way it is? Supercharger belt, tensioner and double pulley were change about 6000 miles ago. Car has 48500 miles. Sound has been present for about 1200 miles.

SICAMG

Mine is a new pulley and the clearance was set perfect. A few hundred miles later ...it's there and will randomly come and go when cold. When the engine get's some work this winter I will take it back off and fix it but for now no worry's.
I could be wrong for you but yours sure sound's like it to me.

Dokus

Interesting, next time I hear it will take a stethoscope to the pulley for closer inspection. I'll report back here of my findings. Thanks for the help

Dokus

The sound have started getting louder which makes me worried. Still haven't found the source of the sound. I've listened around with the stethoscope and at the pulley with no success. I will make a new clip where you can hear the sound better. Any other ideas? Sounds almost like something open/closing made of metal.

MartinWake

Does it sound anything like the sound that happens to mine?

https://mbworld.org/forums/w211-amg/...old-start.html

Dokus

The clicking sound itself is similar to yours but your clicking is mush more frequent. Both my double pulley and SC tensioner is new.

SICAMG

Do this ...run a feeler gauge between the supercharger pulley and the magnet and slowly rotate it and see if there are any high spots where the feeler gauge snags it a little. I think around 25 thou. should work for you. I would focus on this pulley.
Don't go by the fact that your double pulley and tensioner are new because you know how that goes and one may very well be going dry/bad.
If you need spare pulley's to test I can send them to you as there almost new, just cover shipping.

Dokus

Thanks, I will do that tomorrow. If there is a high spot, what to do about it? Leave it alone och grinding?

I still have my old pulley and tensioner so I can test with those but my sound is more like a high spot would cause compared to the other video which is more frequent.

SICAMG

You can just clean up the pulley if needed. Mine has done it and is now doing it again so will have to remove and clean up. Normally you never have to or need to do this but hey....it's mechanical so it happens.

Dokus

So I've removed the supercharger belt and checked the pulley and tensioner, all good. Used a feeler gauge between supercharger pulley and magnet. Found nothing. Sound seems to be gone though, 10 start ups from cold with no sound. Weird.

MartinWake

Yesterday before starting my car I added a bit of oil, once I started it the sound was not there for 10 sec then came again, but if I remove S/C belt sound is gone

testknight

Dokus, Do you still hear the sound with supercharger belt off?

Dokus

I never started the car without the belts, just spun the pullies by hand and used the feeler gauge between supercharger and magnet. Sound have still not reapared for me after several more start ups. No clue what caused it. Maybe dirt between the magnet or something with the belt. Both my supercharger tensioner and double pulley are new as are both belts.