617 Mystery knocking noise help! - video - PeachParts Mercedes-Benz Forum

anarchy · #1 09-20-2014, 01:46 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

vstech · #2 09-20-2014, 09:35 AM

Adjust your valves. Inspect the cam followers, it sounds like cam wear to me.

cooljjay · #3 09-20-2014, 04:20 PM

I won't even bother to look at the videos, knowing the valves aren't adjusted...

If the timing chain is stretched that bad, then it needs to be replaced...that also tells me that the valves have seen very very few adjustments...

fyi....its is soooo not a wise idea to buy one of these cars and being a broke college student, specially having that many miles and for 400$..

Did you have the injectors rebuilt? or did you just toss in another used pair?

anarchy · #4 09-20-2014, 07:35 PM

I just installed a new timing chain the old one had 7 degrees of stretch. I got a set of injectors and pop tested them before installing. I just have not done a valve adjustment because i have always assumed its not really needed unless its becoming hard to start.

cooljjay · #5 09-20-2014, 08:47 PM

Oh lord really? When it becomes hard to start....Did the car come with a manual? You should read it...

So did you install, turbo injectors or non turbo? What brand nozzles? When you pop them did they spray or pee? Change the heat shields too?

Did you make sure that there wasn't a woodruff key installed to help with the stretched timing? re adjusted the IP timing?

There is a lot more to these cars that need doing then gassers..

WOW that engine needs a lot of work, your valve cover is leaking, leaking fuel return lines, original primer pump, and wheres the blow by coming from?

Drago · #6 09-20-2014, 09:30 PM

might have to suck it up and buy a used motor, I spent a lot on mine. even tho I run home made BioD thru it at 1.25 a gallon it will be a long time before I recoup the cost But I do enjoy driving it.

ROLLGUY · #7 09-20-2014, 11:15 PM

It looks like you are leaking fuel around the injectors pretty bad as well. It may just be the lighting, but I would clean (pressure wash) the engine to find the leaks. Normally the valves get tight, not loose enough to make noise. There could be something else in the valve train causing the noise. I had an engine that sounded exactly like that, and it turned out to be a bad rod as the piston was hitting the head.

anarchy · #8 09-21-2014, 05:34 AM

the fuel return line had slipped off causing fuel to pour out, everything is kind of taken apart the blow by is just vent line not being connected to anything. the injectors are from a turbo version, good spray pattern. I had to order a new feeler gauge so I will do a valve adjustment on tuesday when the tool arrives. I will also take a better look at the cam. over all it seems to be in good condition. the noise hasn't become any worse, if anything it has quieted down a bit since I got it. thanks for the input

leathermang · #9 09-21-2014, 08:56 AM

Quote:

Originally Posted by anarchy

.......... I just have not done a valve adjustment because i have always assumed its not really needed unless its becoming hard to start.

Really BAD IDEA..
because....
at least half the cooling for the valves is provided by being in good contact with the head..AS you go towards.... BUT BEFORE YOU GET TO HARD STARTING....
you slowly have less forceful contact between the valves and the head.... thus your likely to BURN VALVES as you get closer to ' hard starting ' symptoms'.....
and you will not know it until the damage has already been done...

anarchy · #10 09-23-2014, 09:31 PM

you're completely correct about cooling being provided by contact with the head. Everyone seems to say that the valves tighten over time but I'm sure they can also become loose.

fahrvergnugen · #11 09-24-2014, 12:06 AM

The valves pound themselves into the head, hence why they get tight.

leathermang · #12 09-24-2014, 01:14 AM

Quote:

Originally Posted by anarchy

........... Everyone seems to say that the valves tighten over time but I'm sure they can also become loose.

The tendency of the valve train to get either tighter or looser over time is determined by the engine design.

anarchy · #13 09-24-2014, 02:16 AM

so check out what I discovered when I went to do a valve adjustment. notice the deep groove cut into the rocker arms from the cam, furthermore check out the rod that runs through all the rocker arms I forget what its called.. it's so deeply scored
I didn't notice how bad the damage actually was until I removed the rocker arms so that I could see under the cam. As I suspected the noise was coming from #3 exhaust using a mechanics stethoscope I noticed the worst damage there.
I'm thinking the best way to proceed is to replace the cam and all lifters that should solve the problem.

https://picasaweb.google.com/117432585961445952638/September232014?authuser=0&feat=directlink

vstech · #14 09-24-2014, 07:43 AM

It is sometimes scary how good I am...

vstech · #15 09-25-2014, 12:39 PM

Quote:

Originally Posted by anarchy

►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.

you may want to inspect the cam on your SD...