Strange 'metal squeal' Noise - 85 300 SD...Suggestions, help plse. - PeachParts Mercedes-Benz Forum

71inka02 · #1 12-14-2008, 10:24 PM

You know what is sounds like when your brakes are in the early stage of 'metal to metal' ---- 2 metals rubbing together, NOT grinding...but a rubbing, or a metel to metal squeal...

This TYPE 'squeal' is what I'm hearing - not extremely loud, but steady and noticeable to me with window partly down, and radio off. And I'm almost positive it's in the front of the car.

The noise I'm hearing is at a variety speeds and when hearing it - I've slightly came off the fuel and it goes away -- I've slightly gotten on the fuel and it goes away.

I've slightly applied brakes while maintaining fuel position --- no change in 'noise'. I've moved steering side to side while maintaining fuel position - no change in 'noise'. Transmission is shifting smooth and perfectly.

For some strange gut reason, I'm thinking turbo?

Looking for help, ideas and things to check. Many thanks in advance...

leathermang · #2 12-14-2008, 10:29 PM

Does it change pitch or loudness at different speeds ?

bgkast · #3 12-15-2008, 12:05 AM

Well, it's easy enough to check the turbo. Pull the U tube (Car off!

) and see if the turbo wheel spins freely. Then gently grip the center nut and try to wiggle it side to side, the amount of play should be barely noticeable. You can also try gently turning the wheel while you wiggle it, it should not scrape the housing.

jt20 · #4 12-15-2008, 02:39 AM

belt tension

turbo

check all spinning accessories for play and free movement

leathermang · #5 12-15-2008, 02:50 AM

So it does NOT make the noise when the car is NOT moving forward ?

71inka02 · #6 12-15-2008, 08:10 AM

First of all --- HOW the H__L do you use the 'multi-quote' feature and address/anwer more than 1 thing in a reply, without having to retype stuff??? Friggin hate Monday mornings!

LEATHERMANG:
No, pitch/loudness does not appear to change, and No I don't notice when car is sitting and idling.

BGKAST:
My question may appear dumb to some, but must ask to make sure I understand --- The U-tube you refer to is 'front/lower' of the air filter housing..large tube, right?

PS....A few weeks back when changing my air filter and looking at and around AF housing to determine if I needed to order AF housing 'mounting' bracket as along with bushings --- I noticed the 'large U-tube' clamp didn't appear tight - When moving housing around, gently - The U-Tube moved freely at it's clamp point ---- Almost appeared it could be pulled off, WITHOUT removing or loosenng clamp??? Clamps typically used to hold things tight --- YES??

JT20:
Didn't check belt tension, and other pulleys, etc.. etc... -- Will do that this afternoon.

nickofoxford · #7 12-15-2008, 09:04 AM

Quote:

Originally Posted by 71inka02

First of all --- HOW the H__L do you use the 'multi-quote' feature and address/anwer more than 1 thing in a reply, without having to retype stuff??? Friggin hate Monday mornings!

x2!!

Check the alternator too, just throwing that out there. Mine really tortured me for a while because the bearings would only have room to rub and make noise when the belts had some speed and the belts loosened up on it a little bit. Also as far as components go the A/C clutch could do the same thing I suppose.

SD Blue · #8 12-15-2008, 10:54 AM

I'm thinking alternator also. If the turbo was making that kind of noise, I would think you would already be seeing significant oil usage and mosquito fogging smoke.

Does the '85 have a serpentine belt?

71inka02 · #9 12-15-2008, 11:22 AM

Quote:

Originally Posted by SD Blue

I'm thinking alternator also. If the turbo was making that kind of noise, I would think you would already be seeing significant oil usage and mosquito fogging smoke.

Does the '85 have a serpentine belt?

No significant oil usage or fogging smoke.

I don't "think", so --- was just looking yesterday, and have brain fog thing going on this morning...

Question: If alternator bearings were bad, or going bad - wouln'd I be seeing signs of that thru typical "alt or battery" warning signs?

leathermang · #10 12-15-2008, 11:25 AM

For some strange reason we have not asked you if you actually checked the brakes..which you said this most sounded like...LOL
Have you checked your brake pads ?

71inka02 · #11 12-15-2008, 11:33 AM

Quote:

Originally Posted by leathermang

For some strange reason we have not asked you if you actually checked the brakes..which you said this most sounded like...LOL
Have you checked your brake pads ?

NO - haven't visually looked -- but, there is no noise when applying brakes...And also, when I hear the noise, I have applied pressure to brakes while staying on the fuel --- No change in noise.

SD Blue · #12 12-15-2008, 02:34 PM

Quote:

Originally Posted by 71inka02

No significant oil usage or fogging smoke.

I don't "think", so --- was just looking yesterday, and have brain fog thing going on this morning...

Question: If alternator bearings were bad, or going bad - wouln'd I be seeing signs of that thru typical "alt or battery" warning signs?

Not always, I have seen cases where initially there was bearing noise but no warning lights. Which sounds very much like what you are hearing.

Something I've tried in the past is spraying a small amount of silicone spray on the alternator shaft area, between the pulley and housing and see if it quietens down. If it's the bearings, you might get a slight break in the noise but will eventually come right back.

leathermang · #13 12-15-2008, 02:42 PM

Quote:

Originally Posted by 71inka02

- but, there is no noise when applying brakes...And also, when I hear the noise, I have applied pressure to brakes while staying on the fuel --- No change in noise.

You have said two different things in one sentence.

You have no noise when applying brakes...
You have noise but it does not change when applying the brakes...

Can you narrow it down a little ?

and you are making some assumptions about the brake pads and rotors which may turn out to not be true...

You have several suggestions now.. just try one at a time so everyone knows which it turned out to be...

harpua00 · #14 12-15-2008, 02:47 PM

might be EGR, or one of the EGR control valves mounted on the left front fender or the vac lines running to one of those components. EGR is activated most under light throttle but not under idle nor heavier throttle. If you go under the front passenger dash and unplug the OVP relay that will deactivate the EGR computer.....if the noise goes away it's something in the EGR circuit.

71inka02 · #15 12-15-2008, 03:07 PM

Quote:

Originally Posted by leathermang

You have said two different things in one sentence.

You have no noise when applying brakes...
You have noise but it does not change when applying the brakes...

Can you narrow it down a little ?

and you are making some assumptions about the brake pads and rotors which may turn out to not be true...

You have several suggestions now.. just try one at a time so everyone knows which it turned out to be...

I see how my writing can be confusing - was attempting to cover all the options---so here:

There is NO brake noise when using brakes - meaning pads and rotors aren't making noise.

When I said - "have noise but it does not change when applying the brakes" ---- Meaning: I'm cruising down the road and the noise is present and In an effort to determine where the noise is coming from --- I apply pressue to brake pedal while keeping throtte position, and the noise doesn't change. Hence, that rules out the noise being brake related, at least it does for me. Does that make sense this time, or did I make it worse???

And I did visually look at the brakes --- pads and rotors are good and all appears fine there.

And also to clarify -- In the start of this thread -- I used the words brake noise, simply as a WAY of describing the noise, thinking - what brake noise 'sounds like' is understood by most.