PeachParts Mercedes-Benz Forum - View Single Post - 617 Mystery knocking noise help!

anarchy · #1 09-20-2014, 02:46 AM

First off I bought this 79 W116 from a recently deceased person so I wasn't able to get any previous information on maintenance.
it has 350,xxx miles on it.
Paid about $400 for the car including registration.
body is straight and in great condition interior is also pretty good.
I'm in college now so money is tight. can't really afford buying a new engine or more expensive parts like timing chains and injectors.

I bought the car knowing that it had a mystery knocking noise, I assumed it was fuel injectors. so I replaced all of them including a pre chamber.
Next I found that the timing chain tensioner was maxed out and 7° of stretch.

►The knocking noise is hardly noticeable at idle but upon acceleration is very prominent.
►I notice that when I start the engine before oil pressure builds up the knocking noise is worse. after pressure builds up the sound quites down.
►Using a mechanics stethoscope the sound seems to be most prominent at the #2 exhaust port.
►Both engine mounts are in good condition.

I can't imagine it being a rod knock doesn't sound deep enough.

►I checked the oil and found very fine metal particles. I compared the oil to my perfectly running 300sd and found there to be the same amount of metal particles.

☼The one thing I have not done yet is a valve adjustment. I assume that because it starts right up theres no need for it. I may be wrong please let me know

▬My best guess is piston slap.▬
if the sound doesn't get worse is it ok to drive?
I just need some help figuring out what to do next.

please watch the videos, the first one is the longest

300SD OM617 Mystery knocking noise Piston Slap? - YouTube
300SD OM617 Mystery knocking noise video 2 - YouTube
300SD OM617 Mystery knocking noise video 3 - YouTube