AMG_RL

Check your Idler pulleys! For the past month I've had an extremely horrid knocking sound which I swore was coming from under the passenger side valve cover. Now we all know how loud our engines are normally, but this sounded like there was a loose bolt inside the valve cover grinding away. It would go away as the revs went up but on idle the noise was unbearable. Anyways, my Indy shop is usually backed up a week or so so i decided to do some investigatng and found that my s/c idler pulley had a slight wobble to it. Upon removing the belt, the wobble was pretty damn significant. I hopped on eBay, ordered a $3 6203zz bearing, replaced the bearing inside the pulley and what do you know...no more knocking!

Just want to point out as well, there was absolutely no other symptoms besides the noise. The car still pulled like normal and drove the same. Of you're experiencing other issues it may infact be valvetrain issues.

Lastly. Many thanks to pearlpower for the awesome DIY, literally saved me a couple hundred $$$ and a bunch of sleepless nights.

desired_speeds

can you link me to the bearing you used?

AMG_RL

This is the one I used: http://www.ebay.com/itm/130692941606...84.m1497.l2649

desired_speeds

thanks! and I just need one right?

AMG_RL

Yes just one, the serpentine belt pulley's bearing isn't replaceable. Here's the DIY also https://mbworld.org/forums/w211-amg/...ng-repair.html

berti_00

or replace the whole set with the ASP set