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..

Barry-

That's why I asked how long he owned the car, as these odometers can tend to find themselves askew of "genuine" miles.....not that that's the case, but it was worth trying to ferret out new owner/new (2u) owner type info....

If you are indeed in KY, I might be able to look at it, schedule permitting.

Otherwise, it could be a loose air filter mount. My rubber isolators broke apart, and made a very loud noise outside the car, like bolts in a dryer, and sounded very low like rod knock from inside the car

Top of the engine all checked out.
Oil drained. Mechanic who is tip-notch, and has serviced this car always for the 3 years I've owned it, will check out the bottom end.

Suggestions what it may be?

Flex disc?

Other?

Does it do while the car is moving, or will it do it while sitting still? Most drive line and rear axle noise will be rhythmic and change with speed, or noises happen during sudden changes in acceleration. Make sure to look at the motor mounts, and the shields on top of the motor mounts. I had a bent on that was rubbing on the body and making screeching noises like belts. Also look at the transmission mount. Could be a look exhaust heat shield, or even the exhaust rattling on something.

It could be the motor mount ( at least it was in my case)
Jon

In a situation like this, a YouTube clip is worth a thousand words of problem description.

Before I took it in, I could drive north of 25-ish mph and the awful rattle would quiet. But as soon as I began slowing down, loud again.

The above shounds a lot like the something loose on the Air Filter or Bracket.

OK the Mechanic going to look at something but where did He say He though the sound was comming from.
Also while He can look and see if there is anything in the Pan there is not too much of the bottem end he can get at from the small Oil Pan.

New air brackets look great.
New turbo parts look great.
Timing chain, valves, everything on top etc look great.
New motor mounts look great.
1.5 quarts low on oil but not remotely catastrophic.
Mechanic going through bottom end tonite and tomorrow.

Flexdisk?

It's TOUGH to diagnose noises and rattles on the internet. The most likely thing would be the vac pump roller. If the sound is coming from that area I would NOT run the engine any more until I removed and inspected the vac pump. This would be a quick job. Those rollers have DESTROYED engines. If inspection of the pump does indeed indicate that the roller is gone, don't just replace the pump. FIND THE ROLLER and get it out of there.

I have had them get pretty noisy with the roller loose, but still attached. If that's what you find, then it's a quick fix.

Is the mechanic familiar with the breed?

Did he remove and check the vacuum pump?:confused:

Did he look at the harmonic balancer and the main crankshaft pulley? In addition to the vacuum pump, those things are known failures which make rattling noises.

Barry and the others who said Flex Disk, you are correct. Although under the car, sounds like from the front. I gave my mechanic a hug when he told me it's not the end of the world (eg, thrown rod), just a cracked flex disk.

Now that the problem has been run down.

I have an interesting one for you. Concerning my naturally aspired 1977 123 300d.. Came out of the cottage one morning. Started it up and heard a very bad sounding rattle.

A word of warning here. Any time you hear a rattle under the hood do not lean over the radiator until you have checked with the engine off that the fan assembley is still intact.

I have cerrtain knowledge that the fan let loose and killed a guy in my neighbourhood many years ago where I grew up. He was simply investigating the source of the underhood noise.

That said once I had quickly checked my fan I started the car again and heard a sound like the flex plate was perhaps the issue. A broken crank kind of makes a clang on startup but does not usually stay noisy once the engine is running.

I was just thinking this is great. Then the noise stopped and never occured again. Not that I am complaining but for the life of me that seemed very abnormal.

It did not sound much like the starter had not totally disengaged but in all likely hood just may have been randomly touching the ring gear on the flexplate. Not much else could account for what I experienced that morning. That it never reoccured again after that second shut down and start is what kind of cinched it for me. More a rattling type of sound than anything I thought.

I think it was one of my very early posts years ago when I posted a thread about it but recieved no reponses. It was only later that I personally concluded there was no other possibility that was logical. I did post that it seemed at the rear of the engine and low on my original thread.

I also have to wonder how the mechanic responded to your hug. They in general do not get that many.:D