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OT -- (car) brake noise
 

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April
Joined: 13 Dec 2003
Posts: 6593
Location: Westchester/NYC

1/19/17 3:15 AM

OT -- (car) brake noise

Not a high-pitched noise. But a low pitch "growl", or grinding like noise. Like there is rust or sand on the breaking surface.

it's only loud enough to be heard with the radio off. Break performance is still good.

What might be a possible cause of that?

Apology for starting another non-cycling thread. Hopefully this one will be short lived.

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Brian Nystrom
Joined: 26 Jan 2004
Posts: 5096
Location: Nashua, NH

1/19/17 6:14 AM

We need more details

When does this occur, during normal driving, when braking, when cornering, when accelerating? Where does it seem to be coming from?

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Dave B
Joined: 10 Jan 2004
Posts: 4511
Location: Pittsburgh, PA

1/19/17 6:15 AM

Have you checked the pad thickness? It could be the wear sensor dragging on the rotor telling you it's time for new pads.

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April
Joined: 13 Dec 2003
Posts: 6593
Location: Westchester/NYC

1/19/17 6:19 AM

Detail

The noise happens when braking gradually.

Car has been serviced recently. Pad thickness was reported to be well within normal.

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Kramer
Joined: 12 Jan 2004
Posts: 121
Location: Richmond, VA

1/19/17 7:36 AM

ABS Pump?

My Subaru has been doing that on and off. The ABS pump is going bad and does it intermittently.

Sounds like a low intensity grinding with a little pedal feedback.

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April
Joined: 13 Dec 2003
Posts: 6593
Location: Westchester/NYC

1/19/17 11:25 AM

Not sure about the pedal feedback part. But yes, low intensity grinding.

Noise goes away once I push down hard on the brake.

Could it be warped rotor also? I had that some years ago and vaguely remember it's also a noise that gradually got worse...

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Pat Clancy
Joined: 13 Jan 2004
Posts: 1353
Location: Manchester, CT

1/19/17 12:50 PM

Rotor

A warped rotor will usually give some sort of pulsing feedback through the pedal or as you gradually come to a stop, it can be felt as a vibration whose frequency drops with the car speed. Do you notice either of those symptoms?

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April
Joined: 13 Dec 2003
Posts: 6593
Location: Westchester/NYC

1/19/17 12:55 PM

It only happens occasionally. So I wasn't prepared to analyze it when it happens. But it's happening just frequent enough that I know I'm not imagining it.

I'm trying to decide if it's worth bringing it in to the dealership to have it looked at. Or just wait to see if it gets worse.

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dddd
Joined: 11 Jan 2004
Posts: 3345
Location: NorCal

1/19/17 1:44 PM

The front brake is like that on my mountainbike sometimes, a low-pitched buzz that goes away as I squeeze the lever harder. It comes and goes randomly, and I suspect it has something to do with the pattern of holes in the rotor, that the metal segments are perhaps subject to heat-induced warpage on an individual basis from time to time. Not really applicable to a car's rotor in this instance.

On my old VW Rabbit, I had a brake rotor that suffered surface delamination, I can't recall the exact behavior of noise versus pedal pressure though "rough" would be the best description of the symptoms.

If it is a rotor defect, whether a surface flake-off or a variation in thickness caused by uneven metallurgy and thus uneven wear, the cyclic frequency should be almost obvious as a once-per-revolution occurrence, roughly every six feet of travel.

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Matthew Currie
Joined: 11 Jan 2004
Posts: 800
Location: Vermont

1/19/17 9:34 PM

My guess is rust on the edge of a rotor. It's very common as rotors age that a band of rust builds up on the outer edge, and sometimes near the center as well, and when it does, it wears the pad a little so the pad does not scrub it off. The pads retract only a very slight amount - there's no return spring, only a combination of tension in the caliper piston gasket and rotor runout, to prevent the pad from dragging, and not enough to get the pad clear of the rust. Usually this noise will change when you apply the brake. If you can see the brake rotors through the wheels, as is often the case, look to see if the outer edges of any are rusty and not shiny. If it's just a little rust on a rotor, you're probably all right just leaving it alone, but keep an eye on things.

Another possibility, if this is a four wheel disk vehicle is the parking brake. Some use the disk for this, but many have a little drum brake inside the rear disks. When those get old, rusty, or start falling apart, they can make noise too. This is easy to check, because if you pull up on the brake handle a little while rolling, the noise will stop or change.

If applying the brake does not change the noise at all, consider the possibility of a bad wheel bearing. On a disk brake car when a wheel bearing gets bad enough, disk runout will push the brake pads back too far, and you'll get an intermittent soft pedal, and possibly rather serious pull to one side. Noise from a bad wheel bearing will usually change on curves. A rusted rotor might change a little when cornering too (things flex more than you'd think) but not as much.

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April
Joined: 13 Dec 2003
Posts: 6593
Location: Westchester/NYC

1/20/17 8:27 AM

Don't think it's a bad wheel bearing. I had that in one of my cars once. This one doesn't have any steering feedback associated with the noise.

I'll look for rust on the rotor once I'm back to be with the car. That sounds just about right. If that turn out to be the case, would it wear down the pad excessively as a result? If there's such a potential, I'd better get it taken care of, right?

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Sparky
Joined: 08 Dec 2003
Posts: 19068
Location: PDX

1/20/17 10:03 AM

I get something similar when the car sits out in the rain for a few days. Rust forms on rotors but usually after some miles of brake use it subsides.

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April
Joined: 13 Dec 2003
Posts: 6593
Location: Westchester/NYC

1/20/17 11:26 AM

Oh, that could be IT!

I was in Hong Kong for Christmas AND New Year. So between that and my not using the car during the week prior to leaving for the orient, the car's been sitting unused for nearly a month! (in the garage though)

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Sparky
Joined: 08 Dec 2003
Posts: 19068
Location: PDX

1/20/17 11:29 AM

Humid in the garage?

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April
Joined: 13 Dec 2003
Posts: 6593
Location: Westchester/NYC

1/20/17 1:08 PM

not really

but who knows

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dddd
Joined: 11 Jan 2004
Posts: 3345
Location: NorCal

1/20/17 1:49 PM

Even with the car left in the rain sitting for weeks (I've done this countless times), the rust on the rotor rubs off usually within one stop. The pads though are hygroscopic and may take several stops to stop being grabby or noisy as the moisture is driven off by heat. I don't think either of these are your problem though, since I am assuming you've driven at least a few miles by now(?).

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April
Joined: 13 Dec 2003
Posts: 6593
Location: Westchester/NYC

1/20/17 5:26 PM

I've driven a few miles last weekend. That's when I noticed the noise.

Car sits in the garage again during the week. (I'm with the car now. But it's already dark)

I'll be able to look tomorrow morning. Also, I'll be driving it tomorrow and will see if the rusty noise goes away by itself if that's the case.

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