A Most Terrible Noise - PeachParts Mercedes-Benz Forum

ctsoth · #1 10-10-2008, 09:56 AM

Miles: 185,000
Year and Model: 84 300D Turbo, Automatic.

From the front of my engine comes a noise which is most disconcerting. I think that maybe a timing chain tensioner has bit the dust and now the chain is grinding over metal.

The front of my engine sounds that bad. Is it possible that I am on the right track or could this terrible awful "your engine belongs in engine purgatory" sound be something else.

The facts of "the sound."

1. Started last night.
2. Comes from front of engine
3. Is loud. Loud in the cab even.
4. I am having a hard time describing this sound, but it to me sounds like it could be chain related.

The final and most important fact:

5. The car is parked, I do not want to turn it on again. I am afraid of what could happen.

-Chris

rrgrassi · #2 10-10-2008, 10:08 AM

Could also be an AC compressor Idler pulley, Alternator bearings failing, power steering pump, water pump, fan clutch, or vacuum pump.

Also check the harmonic balancer. Pull the valve cover and check the chain for marking.

Also, remove all the belts and spin the accessories by hand, including the water pump, and listen for noises.

If this does not reveal the sound, use the crank bolt and turn the engine by hand and listen for any noises.

My car had a situation like that, and it turned out the be the A/C compressor clutch/idler pully.

jt20 · #3 10-10-2008, 10:09 AM

constant?
intermittent?

why do you think it is the chain?

try turning the engine by hand. Youl be in a safe position without the engine running so you can get a better idea of the noise source. Make sure to include the vacuum pump as part of your inspection.

ctsoth · #4 10-10-2008, 10:28 AM

It is a pretty loud noise, the vacuum pump seems like it would be too small to produce this but I will check it out.

Thank you for the suggestions, time for an investigation to begin. The alternator is a fresh rebuild, it had the bearings replaced on the rebuild. I had it done at a local shop that my family has used many times before. We have never had a problem with their alternators, but as it is a recent change there is certainly a chance of error here.

jt20 · #5 10-10-2008, 10:35 AM

pulling the valve cover and the tensioner that goes to the banana slide rail is the easiest way to get a good inspection of the chain and many of its contact points.

rrgrassi · #6 10-10-2008, 10:36 AM

The little fan on the alt can also rub and make noise if the alt shifts towards the engine.

Was the noise gradual or all of a sudden?

Yes, vacuum pumps can get noisy as the are driven off of the timing chain. If they puke out thier parts, it usually causes the timing chain to break, resulting in replacement engine time.

Charlamu had a timing chain break...

But, before worrying about the chain, lookk at all the other areas first.

ctsoth · #7 10-10-2008, 10:42 AM

All of a sudden. Wasn't there when I left last night but was there when I got to my destination.

It is pretty loud, and it is constant not intermittent. The sound really does remind me of a chain being drawn over metal, and I am fairly certain I heard a few metallic "pings" while the engine was idling. I heard this ping once or twice, but I can not swear by it. This ping was not loud.

I am not at home either right now, so I do not have access to tools... I will keep answering questions and find ways to pass the time.

rrgrassi · #8 10-10-2008, 10:45 AM

The metallic pings may have been the beginning of the noise.

Stuff does get loud under the hood, due to hollowed engine cavities and the acoustics of the engine bay. Something really minor can sound like a major player.

ctsoth · #9 10-10-2008, 10:49 AM

Quote:

Originally Posted by rrgrassi

The metallic pings may have been the beginning of the noise.

Stuff does get loud under the hood, due to a hollowed engine cavaties and the acoustics of the engine bay. Something really minor can sound like a major player.

Ooo, thank you. That makes me very happy, although I will try not to get my hopes to high or low.

EDIT:

I feel sorta stupid for not adding this earlier, but last night I did drive the car a short distance after the appearance of this noise. I did not notice the sound in operation, only at idle or very close to idle. I mean to say that the car sounds fine going down the road. I recognize driving it that short distance was an error in judgment.

And also, like I said earlier, I am hesitant to even start it but I recognize that I very well may have to.

rrgrassi · #10 10-10-2008, 11:23 AM

That is exactly how the A/C clutch pulley started out, then it was a racket even on the highway. I stopped driving the car also until I replaced the A/C compressor.

ctsoth · #11 10-10-2008, 11:27 AM

Well ****, it's the harmonic balancer.

That sorta puts me in limbo. I know there will be damage to the end of the crank. I had an issue with the balancer in the past but it never made a sound like this before. It came loose 1,500 miles ago but the crank only showed slight wear and the fix was solid. I figured it would come loose again someday but I really expected it to last longer than this.

Never remove the harmonic balancer for any reason. The owner of Munich Motors informed me that balancers NEVER come off if they haven't been tampered with since leaving the factory. Correctly mounting the harmonic balancer is a very intricate operation which must be undertaken with the utmost precision.

It is apparent to me that the harmonic balancer has been off the car at some point in its past, as the radiator fins have some light damage in front of the crank bolt. So there is physical evidence that someone has been in there before. Munich Motors informed me that what most often happens; is people will have the front pulled to fix an oil leak. He was adamant that people should never do that.

rrgrassi · #12 10-10-2008, 11:39 AM

Did it shear the pins? If not, that is a good thing. I did have one fail on an Olds with the Quad4 engine. It was a PITA to replace thanks to no space due to the tranverse mount FWD setup.

Either way, do not drive it or start it up. Have the car flat bedded home if you are away from home.

You will have to remove all the belts. I would suggest to remove the fan and shroud also to give more room.

ctsoth · #13 10-10-2008, 11:42 AM

Reposted from Edit:

I know there will be damage to the end of the crank. I had an issue with the balancer in the past but it never made a sound like this before. It came loose 1,500 miles ago but the crank only showed slight wear and the fix was solid. I figured it would come loose again someday but I really expected it to last longer than this.

Never remove the harmonic balancer for any reason. The owner of Munich Motors informed me that balancers NEVER come off if they haven't been tampered with since leaving the factory. Correctly mounting the harmonic balancer is a very intricate operation which must be undertaken with the utmost precision.

It is apparent to me that the harmonic balancer has been off the car at some point in its past, as the radiator fins have some light damage in front of the crank bolt. So there is physical evidence that someone has been in there before. Munich Motors informed me that what most often happens; is people will have the front pulled to fix an oil leak. He was adamant that people should never do that.

Also, the pins did not sheer. The balancer is vibrating loudly but it is still being held by the pins. I don't dare to start it again.

rrgrassi · #14 10-10-2008, 11:51 AM

Did the crank bolt work it's self loose? I do not see how it could based on engine rotation, but people have loosend the crank bolt by leaving a breaker bar and 27mm socket on the crank bolt, and bumping the starter.

I have never heard the warning to "never remove" the HB.

Sounds like you might be able to get away with replacing the HB and keep rolling down the road.

vstech · #15 10-10-2008, 12:37 PM

How about some green Loctite on the crank snout, and some red on the Crank bolt. I know it's a really bad thing to do to someone, but that stuff should hold it on for a while.
yes? no?