Squealing/Screeching noise. - Page 2 - PeachParts Mercedes-Benz Forum

GaryF · #16 10-25-2009, 06:20 AM

Quote:

Originally Posted by Graham

Switched to a spare distributor today. I did not drive car very far, but I think I may have noise still. It now only comes when I accelerate mildly at relatively low speed. But it is same louder noise that I originally heard at idle too.

I found that coolant level was lower that it should be. Filled it. I thought that maybe there was air in system from when I pulled AAV a week or so ago. Again. no conclusive test.

Belts are quite tight, but I thought I would tighten more and see if I could make noise happen again at idle. But, Alt adjuster is tight - soaking it overnight with Release-It.

Not sure how I would check cam bearings?

Maybe your belts are too tight and stressing the bearings, as GGR suggested run without the belts for a short time to eliminate accessories rather than tightening the belts further. If it was a cam bearing you would be able to locate a lot easier than you have suggested

GGR · #17 10-25-2009, 07:53 AM

I usually have my belts a bit looser than they should as accessories bearings are older. That prolonge ther life quite a bit. Overtightening the belts may spoil the bearings much quicker than on a newer car.

Graham · #18 10-25-2009, 09:03 PM

Quote:

Originally Posted by GGR

I usually have my belts a bit looser than they should as accessories bearings are older. That prolonge ther life quite a bit. Overtightening the belts may spoil the bearings much quicker than on a newer car.

Mostly worked on winterizing boat today, but did drive car - no change - still some noise on slight acceleration that goes away if I take foot off pedal.

I ran car as low rpm as I could tonight at idle so that it ran very quietly. I could hear a kind of moaning sound! But, at least it was there all the time. I listened all over and I think it IS coming from the alternator. I can hear it clearly with stetho and when I speed engine up, it goes away. Can't be sure if this is THE other noise I hear or not. Have not loosened belt yet, because adjuster still won't budge! Try again tomorrow.

The alternator is still doing it's job, but maybe bearings are starting to go and that is what I have been hearing? Other than dismantling it or just replacing it, I guess there is no way to know for sure?

mgburg · #19 10-25-2009, 10:47 PM

Can I throw an item in for consideration?

How about the A/C pulley?

It's ALWAYS riding on bearings, whether you have it engaged or not...

Did you "steth" it yet?

Mine just plain locked up solid and THEN you heard some squealing/screeching ALONG with some major smoke...

Just $0.02 of brain matter...

Graham · #20 10-25-2009, 10:49 PM

Quote:

Originally Posted by mgburg

Can I throw an item in for consideration?

How about the A/C pulley?

It's ALWAYS riding on bearings, whether you have it engaged or not...

Did you "steth" it yet?

Mine just plain locked up solid and THEN you heard some squealing/screeching ALONG with some major smoke...

Just $0.02 of brain matter...

A/C doesn't work so I have removed belt.

PS: I had the clutch on my 300D lockup - It was glowing red and stalled the engine. Had to cut belt to get home.

Graham · #21 10-29-2009, 05:14 PM

No real progress on this.

I have replaced the belts, rebuilt the alternator while I was at it (incl new bearings), checked the water pump and PS bearings for any slack (none). Distributor was swapped for a spare.

But noise is still there - exactly same sound as before which tells me that it had nothing to do with the things I have worked on.

It originally occurred at idle, but now only when I am driving. It is quite loud at times and at others just a chirping sound. It happens if I accelerate at low speed and goes away as soon as I take foot of pedal. But it does not do this when I first drive it - it happens as car warms up and then lessens after a longer period.

I now doubt it has anything to do with belts or rotating accessories.

And if it was in engine, you would think I would hear it at idle and/or when speeded up.

Car also has a driveline vibration that happened at about same time. may be related.

I am now going to check torque on new engine mounts, install tranny & diff mounts and check that torque converter to engine bolts are tight.

Otherwise, running out of ideas

Tomguy · #22 10-29-2009, 06:35 PM

Can you record the sound with a digital camera or something & put it on Youtube?

Graham · #23 10-29-2009, 07:05 PM

Quote:

Originally Posted by Tomguy

Can you record the sound with a digital camera or something & put it on Youtube?

I have a video camera and have been thinking about that. Seeing I don't need pictures, maybe I can do it with my old iPaq - It will act as a digital recorder and perhaps I can convert the sound to an MP3 or something. Will look into it.

meltedpanda · #24 10-31-2009, 08:09 AM

you dont think it is an air intake noise do you?
suction noise?

Graham · #25 10-31-2009, 11:16 AM

Quote:

Originally Posted by meltedpanda

you dont think it is an air intake noise do you?
suction noise?

No, I don't think so but I am going to remove a restriction that I put in the AAV hose. The sound is like rubber on metal or metal on metal and frequency varies with engine speed. Anyone hearing it for first time would guess at a belt slipping or a bearing that is failing.

Originally it occurred at idle in park and didn't seem to be coming from engine itself or anything up front. Now it only occurs once engine warms up and that is after about say 5 miles of driving. It happens on slow acceleration and will keep making sound until I take my foot off pedal. And then, I may or may not get it to repeat noise right away.

It originally happened all of a sudden and was very loud and continuous. Since then, it has gradually lessened in intensity and now only happens under way making it very difficult to locate. But it is the same noise.

I also have a driveline vibration that is new. This may or may not be related.

I tried to record sound, but so far not too successful.

Current plan is to first check new engine mounts are installed and torqued properly, install new transmission and diff mounts (both needed anyway). Also check flex disks and prop shaft mid bearing while I am about it.

Also thinking about pulling water pump and seeing if something perhaps has lodged between the impeller and casing. But, should order new hoses first. Don't really want to do this until I get some sign that is where noise is coming from.

meltedpanda · #26 11-01-2009, 09:52 PM

can it be heard outside the car, or only sitting in it
I drive between two buildings with windows open, that some times increased the volume of the noise, of course only if it is making it ( the noise) at slow speeds will this help