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New Noise from 300D Engine.

3K views 17 replies 7 participants last post by  MBGraham 
#1 · (Edited)
I posted this on Peachparts diesel forum but thought I would repeat it here for those that don't go there.

I have owned this car (85 300D) for over 20 years, so I know what the diesel normally sounds like. But today, I noticed that it was noisier than normal and the sound was not the usual klakety klack of the diesel.

I probed around with stethoscope, but so far haven't found any specific source of the noise. It seems to come from everywhere!

This link is from engine bay

https://www.dropbox.com/s/om22ot81s6472x1/MVI_2019.AVI?dl=1

and this one from side of car (less normal engine noise)

https://www.dropbox.com/s/lhp4ns90k9zdnh7/MVI_2020.AVI?dl=1

Any ideas?

Plan is to adjust valves, because that job is due anyway, but not sure that is the problem.
 
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#3 ·
Engine mounts? My car ran quiet one day, and rattled something fierce the very next, as the left side engine mount cracked open.
 
#4 ·
The left side mount on my car is not in good shape, so it was one of first things I looked at. But I could not discern any noise coming from there. But it's a good point and I will check again. The chirping noise that can be heard above the diesel clatter is the one that seems new.
 
#5 ·
I think it is more likely to be a utility item issue rather than an internal engine problem (as said on peach parts too).
 
#7 · (Edited)
You were right Stretch, thank goodness.

As posted in more detail on PP, Diesel forum, I can make the noise go away by spraying water on the belts while running. According to Gates, this indicates slipping belts.

At present trying to tighten belts, but I should probably replace them. But, the adjustment bracket is deformed and I should really repair it or get a new or good used one before pulling things apart.



Anyone have a pic of what the bracket should look like? OK, I think I found one. Maybe I can just bend mine back to proper shape?
 
#6 ·
If what I am hearing is a chirping noise my experience would be to look in the direction of a bearing.Maybe on an alternator or pump, something run by the fan belt.
Also have had belts chirp. With the engine off rub some bar soap on the inside of the belt
and as it runs through the pulleys the noise may go away.
Metal to metal will cause chirping. Check those motor mounts or something loose, grab a hold of the air cleaner, that's where my rattle was coming from.
Just some random thoughts, keep us posted.
 
#8 ·
It looks like everything is in place so you should be able to just bend it back into place.

I ended up doing a ghetto fix with an eye bolt on the tensioner since I couldn't find a good one at the junkyard. That reminds me I still need to find one of those brackets someday, although my ghetto fix is holding just fine for the moment.
 
#9 ·
It looks like everything is in place so you should be able to just bend it back into place.
Looks like I will have to thread the adjustment rod all the way out in order to get the nut out of the way, so I can bend the bracket back.

I would like to do this in place, if I can.

Don't know how practical it will be, but I guess i will find out!
 
#10 · (Edited)
That piece of engineering was unfortunately the worst aspect of an otherwise good design.

I was compelled to buy a new bracket as well recently (from Mercedes, part number and all), and I had my hands full trying to install the thing because of subtle differences between the old and the new. Only partially solved the alternator bearing life problem - alternators just don't seem to last on my car...

Wished the M110's system could fit on the OM617.

 
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#12 ·
I guess the later W123s have the new and improved model - maybe designed by the MB Electrical department? :eek:

Need to get out there and fix that bracket, but can't find my sledge hammer :(
 
#16 ·
Glad you found a simpler fix for your motorcar.
Thanks. By the way, I do have the belts off (waiting for new ones) and have checked the alternator and pump for any noise or play. But they seem good.

The bent bracket could throw the alternator pulley alignment off a bit. I now have it pretty well straightened, so hope that along with new belts will get rid of noise.

Another possible cause of squealing could be that I had been working on rust restoration for about a year (Now almost complete). Car was not driven much during that period. Could be light rust on pulleys could cause belts to slip. Hard to get at them, but trying to clean with steel wool.
 
#18 · (Edited)
Had the noise come back recently on 300D. Sprayed water on and noise went away briefly. Belts were a bit loose, so tightened. Noise still there. Time for new belts, I guess. Found this thread to determine how old they are: 4 years. Would have expected longer! Maybe they would last longer if kept tight!
 
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