Awful engine rattle
 

Sounds like bolts in a dryer.
Limped car to mechanic.
He tried to brighten the mood, "the rest of the car is so cherry, if all you need is a new engine ..."
The Silver Bullet (1979 300SD with just 130k) is in the shop. I hope the verdict isn't catastrophic tomorrow.

Failed harmonic balancer?

if failed Harmonic Balancer, how bad ?

Not that bad. Could be a failed vacuum pump too I think. Not sure if a failing early double diaphragm style pump rattles or not.

if a failing vacuum pump, wouldn't lock/unlock doors etc be affected?

Answer
 

No, if the bearing fails = the spring loaded arm still drags around the face of the timing device pumping..



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In my experience, Mercedes get noisy rattliing sounds when they need maintenance. Usually not too expensive if you do the repair yourself. Oftentimes, it's the air intake system rattling around.

this sounded like something loose under the valve cover

any one adjust valve recently? I have had lifters fall of their perch when I was new at adjusting valves

Cejpat- Is this an (independent) Mercedes mechanic? Has he done work to the car for you in the past and how long have you had the car?

Hate when they jump to the "new motor" solution so quickly.....even if only to make you feel better.......

Is it there at all RPM and temps or does it go when reved or warm? If it goes away it could be injector nailing, and could just be a bad injector. It could be this even if it does it all the time though too, depending on how bad the injector is.

Need to use a stethascope to pinpoint the sound in a case like this.

Do not assume the worst until you have the facts.

I had the same experience... twice. First time was the same sound you describe. Two mechanics who listed to it said I needed a motor. A third, already drunk as a skunk (it was a Friday afternoon) walked up, listened, and pointed to the alternator, then told the other two what they used for brains.

And the answer was: alternator bearing failure.

Second time, I self-diagnosed a bearing failure (it was a more subtle knock) and sold the car the next day for $350.

And the answer was: injection pump failure. Car is still on the road today, with a rebuilt pump installed.

Hmm
 

My first suspicions:

#1. Valve adjustment bad or failed adjustment locking nut.

http://www.peachparts.com/shopforum/diesel-discussion/107729-valve-adjustment-om615-616-617-fyi.html

#2. Injector nailing.

http://www.peachparts.com/shopforum/diesel-discussion/74137-strong-nailing.html

http://www.peachparts.com/shopforum/diesel-discussion/211750-injector-heat-shield-nozzle-prechamber-collar-nailing-link-thread.html

http://www.peachparts.com/shopforum/diy-links-parts-category/142405-diesel-injection.html


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X2 on listening to where the sound comes from.

When the Air Filter Bracket/Air Filter Housing is loose or broken it sounds like something is going to come off of the Engine.

I had a rattling sound in the front of the Valve Cover and it turned out the small upper Timing Chain Guide (#89 in the pic) was loose. Tightend the Bolt up and no more issues for over 4 years.

If they suggest something really expensive I would get a second opinion. That is unless it is sane and obvious and reasonable to repair.

I hope you know this shops general reputation. Certainly an engine at 135k miles can have serious issues but not that common if the milage is indeed accurate. You do fuel the car yourself? If not someone loading gas into it might not be very good. I am unaware if it would make the sounds you describe though with bad or unsuitable fuel..