What is this noise??? - PeachParts Mercedes-Benz Forum

indybenz · #1 06-09-2013, 08:33 PM

Here is a quick video of a troubling noise. It has been getting progressively louder, but that progression has taken many months, perhaps as long as a year. I'm hoping someone will hear the sound and immediately know what it is. Ok, perhaps that's unrealistic...but it does happen occasionally so I'll hope for the best!

I've pretty much narrowed it down to something related to the fan or the balancer (?). The main crank seal is not great and leaks oil which sprays around in there and covers things eventually. I plan on R&R that when I pull the motor this summer.

Thanks for any suggestions.
Indybenz

mach4 · #2 06-09-2013, 10:09 PM

Fan (actually the viscous coupling) is pretty easy to check. Just take it off. Make sure you put the bolts back in and snug them up so the pulley doesn't come flying off. You'll know within 10 seconds if that's it... and it's an easy fix.

Then go through and start checking other candidates - alternator, power steering, water pump, vacuum pump, A/C compressor. Those components can be checked out by using a mechanics stethoscope. Just put the probe on each component and listen. If it's none of those, then maybe go lower and investigate the balancer, etc.

Good luck.

indybenz · #3 06-09-2013, 10:22 PM

Hey thanks Mach4. I've already eliminated the other items you mentioned as culprits over the past several months, so looks like it's the fan or balancer! I'm assuming you mean take the fan off, reinstall bolts to avoid flying pulley, start engine and listen?

Stretch · #4 06-10-2013, 04:34 AM

You can remove the fan and then put the same bolts back in to hold the pulley back in place. Space the bolts with washers so that they don't scrape the water pump housing behind. I think the viscous coupling on the fan can be damaged if it isn't kept vertical (or something like that).

It is difficult to pin point the origin of the sound in your video - my money is on the alternator at the moment - but that could change!

mach4 · #5 06-10-2013, 12:19 PM

Quote:

Originally Posted by indybenz

Hey thanks Mach4. I've already eliminated the other items you mentioned as culprits over the past several months, so looks like it's the fan or balancer! I'm assuming you mean take the fan off, reinstall bolts to avoid flying pulley, start engine and listen?

^^What Stretch said.

pmckechnie · #6 06-10-2013, 12:44 PM

Remove belts, one at a time. Start the engine after each belt is removed and see if the noise is gone. If the noise is still there after all the belts are removed, look at balancer problems or possibly a timing chain tensioner causing the chain to hit the valve cover or front cover.

Paul

rscurtis · #7 06-10-2013, 01:29 PM

Get rid of that air filter while you're in there too. There is no substitute for the factory paper filter element.

cooljjay · #8 06-10-2013, 01:35 PM

Quote:

Originally Posted by rscurtis

Get rid of that air filter while you're in there too. There is no substitute for the factory paper filter element.

+1 and that afterwards looks clogged...

fender_bender · #9 06-10-2013, 02:09 PM

My alternator sounded kinda like that right before it locked up and shredded the belt which left me stranded 400 miles from home.

Stugist · #10 06-10-2013, 05:22 PM

Quote:

Originally Posted by fender_bender

My alternator sounded kinda like that right before it locked up and shredded the belt which left me stranded 400 miles from home.

^ This. Check all the bolts that could come in contact with that fan. I recognize that sound; one of the mounting bolts for my alternator backed-out when I was the freeway one day. Didn't sheer it off, but damn it was a scary sound.

indybenz · #11 06-24-2013, 09:35 PM

Well here's a video of the sound...with the valve cover off. I *thought* oil would not go everywhere. Man I was wrong. Oh well. Now I know!

Also, I took off the belt for the power steering and there is still a 'squeek'. The alternator has been changed and a new belt installed. The sound is still there, both the 'squeek' and the 'tapping/clanking' sound. I thought perhaps the pulleys were colliding with each other as the clearances are minute. But I'm not sure.

Dumbfounded. Just don't want to grenade this motor...it's the best part of the car and is slated to go in a 240 that is much better looking :-)

indybenz · #12 07-01-2013, 05:37 PM

So no reactions to that video, eh?! Was it so offensive that nobody wanted to comment :-)

Sorry the lighting was poor.

Now I've added a squeaking sound that is pretty much constant. It sounds like something is not getting oiled properly...perhaps the vacuum 'roller'? I just put a newer vacuum pump on it recently, and it made the sound before and is still making the same sound, so I don't believe it's related to the pump.

Is there a mechanism that 'feeds' oil to the vacuum pump? Can it somehow *not* get oil? Or is that an impossibility given the way it's designed?

This video should reveal some light on the noise, although now it's turned into a full blown screeching noise:

vtmbz · #13 07-01-2013, 06:08 PM

I had an alternator pulley that behaved a lot like your sound clips. You said you replaced the alternator but did you remove and reuse the pulley? MB has a funny pulley system on the alternatort with a keyway that gets beat up. That makes the pulley wobble and screech. Cheer up, this is going to declare itself very soon. It sounds like one of the pulleys is behaving badly.

indybenz · #14 07-01-2013, 06:18 PM

Well the crazy thing is that I took the alt off of my 240, which has one 'loop' for the belt vs. the two that the other one had, and the noise is *exactly* the same. So unless they both had the exact same problem, I'm thinking it's not the alternator or anything related to it. I could be wrong. And I've had the car up on the lift with the motor running, and the noise comes from the front of the motor, like it's either vacuum pump or timing chain or balancer related. I thought for sure it was the water pump, so I replaced it. Nope! That wasn't it.

So what is this 'keyway' of which you speak? The alternator pulley seems very tight/no play or wobbling that I can tell.

whunter · #15 07-01-2013, 06:34 PM

The full blown screeching noise is:
* A loose belt
* Failing alternator (drag)
* You got grease / oil on the V-face of the belts and they are slipping.

If it is a greased belt, a cheap bar of LYE (or any) soap eliminates the horrid sound.

Going out on a limb for this one; The sound from the first video is:

#1. The alternator and/or pulley
#2. The harmonic balancer pulley mounting screws are failing (allowing the pulley to rock / shift).
#3. The harmonic balancer is damaged, rocking / shifting on the crankshaft.

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