bergfurher

I have a problem I cannot figure out with my 2002 clk320, 120,000 miles well taken care of, I am a porsche mechanic with 30 years experience. It's a knock, on the passenger side only, at the cylinder head where the valve covers meets. Only there. The knock is low pitch, not a higher pitch like a lifter, and again, it's at the head. The noise speed is slow, at idle it's two knocks per second. Does not matter if its hot, cold, warm same sound and it's been there for 4 plus years, only recently it seems a bit louder now. Oil changes, different weights make no difference to the sound. It's right where the chain ramp and tensioner are roughly, I replaced the tensioner, and no change. It's not a lifter sound, but lower pitched. It's a knock for sure, several have said it sounds like a diesel. Experience with older Porsches and chain slap tells me it's not the chain, but not with this as a lower pitched sound, but maybe MB makes these sounds. Seems odd there's a problem with the chain with this mileage. I have seem many you tube videos with cars having the same sound, but no replys or comments as to what it is. If it was the chain, why the slow knock noise, if not I have no clue what this is. Oddly, I have a 2003 s430 that makes the exact same noise in the exact same noise, with 145,000 miles on it. Help.

exhaustgases

Did you isolate the noise? Stethoscope? And it does the knock all the time at all speeds? Exhaust leaks can be misleading and sound like a knock.

bergfurher

I did, it's right at the cylinder head, front left corner on the passenger side, right at or near where the valve cover attaches to the head. Both my mercedes make the exact same noise in the same place.