Knocking noise in 1983 300d - PeachParts Mercedes-Benz Forum

qwerty333 · #1 01-11-2018, 12:27 AM

There seems to be a knocking noise coming from the top/front part of my engine, but I can't seem to pinpoint exactly where it's coming from. Has anybody heard this noise before?

The sound gets faster as the engine RPM's go up, but doesn't seem to affect the performance at all. There is also no vibration at all.

Not sure if you'll be able to hear it properly in the video, but in person, at Idle it sounds like a marble in a empty beer can being shaken every 1 second. It also reminds me of the knocking sound effect that you hear in a movie when a car breaks down on the side of the road while steam pours out of the hood

https://www.youtube.com/watch?v=GQ0Ij9EpX6E

https://www.youtube.com/watch?v=2-0P84eubFo

The car is a 1983 w123 300d turbo

Diseasel300 · #2 01-11-2018, 12:30 AM

I'd suggest not running that engine again until you find the culprit. It would be a good idea to check the vacuum pump, if it grenades it can take your engine with it. Check the driven accessories (water pump, alternator, A/C, P/S pump) for movement or ruined bearings. Look to see if the crank pulley is loose, there was a thread recently here about one that worked loose.

chasinthesun · #3 01-11-2018, 01:18 PM

Sounds right,armature broke and its riding around on the surface putting a nice grove .Youll need to drop the pan to retreive various metaLparts also if it is the vp.Try to gather all the evidense .I had this happen put the pump only lost the bearings and case,with no bearing it was eventually going to end up with a broken arm by wear,caught in time.Theirs around 12 small bearings in that case.

Diesel911 · #4 01-11-2018, 01:43 PM

I was not able to listen to the attachments but if your Air filter bracket mounts on the Engine check that to be sure it is not broken or the rubber buffers are still good.

oilslick · #5 01-11-2018, 03:12 PM

Quote:

Originally Posted by Diesel911

I was not able to listen to the attachments but if your Air filter bracket mounts on the Engine check that to be sure it is not broken or the rubber buffers are still good.

I know you couldn’t listen to the clips, but that’s NOT air cleaner mounts...not by a any means.

BillGrissom · #6 01-11-2018, 03:30 PM

x2 on the vacuum pump. I had a similar sound in my 1985 300D. Forgot how I decided it was the pump, probably using my HF stethoscope (i.e. screwdriver to ear). The pump arm had worn half thru in 150 mi of driving since my son first heard it. A bit more and the parts would have slid into the timing chain w/ disastrous results (happened to a poster here a few weeks ago). I found most of the little balls from the failed bearing in the oil pan.