Grinding Knocking noise when applying brakes lightly - Chevy Impala Forums
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post #1 of (permalink) Old 08-13-2019 Thread Starter
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Grinding Knocking noise when applying brakes lightly

Just notice a kinda grinding/knocking noise in front of car when applying brakes lightly. Tried looking through wheels at pads and they seem like the have plenty of meat left. Car has just 50,000 miles. 2015 LT Midnight Edition
Any thoughts?
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post #2 of (permalink) Old 08-13-2019
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Originally Posted by PhantomRider50 View Post
Just notice a kinda grinding/knocking noise in front of car when applying brakes lightly. Tried looking through wheels at pads and they seem like the have plenty of meat left. Car has just 50,000 miles. 2015 LT Midnight Edition
Any thoughts?
The traction control system applies the brakes when it thinks a wheel is spinning, and it makes a distinctive grinding sound. Did you have the steering wheel turned when this occurred? An intermittent connection in the wiring from the wheel speed sensor to the computer can make the computer think the wheel is spinning. The wires sometimes get damaged by the flexing that occurs when the suspension travels up and down. And turning the wheel can cause the damaged wire connection to become intermittent.

As for the knocking sound, is this the same sound, or a separate sound from the grinding?

The ABS, which rapidly pulses the brakes to unlock them, makes a sort of repeated knocking sound. Again, a damaged speed sensor wire can cause the ABS to kick in.

So, the intermittent wiring can cause both the traction control and the ABS to kick in. (One or the other, but not both, on a given wheel.)

Did you see any dash lights come on when the noise occurred? The traction control usually has an accompanying dash light, but it comes and goes - it doesn't stay lit. It goes out after the traction control disengages.

Low speed, parking lot maneuvering seems to be a common situation for the grinding noise to occur.

Doug

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Iíd like to add some comon sense here.

Due to the wheel turning suspension bouncing creating failure problem. DONT turn ur wheels or hit bumps. Haha j/k was to easy


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Hi Doug,
No lights on dash and turning wheel back and forth does not alter the sound at all. However, it does not make the sound when going in reverse, only going forward.
My best guess is warped rotor, as I do have some pulsing in pedal when coming to a fast stop but not horrible.

The sound goes with the rotation of the tire, like bad spot on a rotor, the faster you are moving the quicker the sound goes, it also goes away once the pedal is depressed more, it only occurs at light pedal pressure.

I tried to look the best I could with a pen light and I seem to have plenty of brake pad left (at least on the outboard side of the rotor).

The sound just started out of the blue today, and I thought about just ordering new pads and rotors, but the car only has less than 50,000 miles, but I guess it's possible the rotor is warped??

I just don't want to waste money chasing a problem if it might be something else. However, I must assume it's brake related if the sound only comes on when applying the brakes. Or am I wrong?
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Could be something as simple as a pebble stuck between the brake and rotor.
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If your caliper or calipers are bad. You could be wearing out one side of the pad and the other is not getting any wear. Happens a lot with messed up calipers.

Iíd take my car into a shop. Just on ur normal oil change and tire rotate. And get a full brake inspection when doing so. Donít go to a dealer. Go to a respectable shop to do this. Dealers tend to sock u with every quote under the sun.


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tj, I do my own oil changes and brakes etc., the car is do for an oil change this weekend, so while I am at it, I guess I will pull the tires and take a look at the rear pads for wear. I might even call and see if our local O'Rileys does resurfacing of the rotors and may just go ahead and throw new pads on it as well.

ICUBB, I thought that as well at first, but not so sure now, that's why I found the sound went away in reverse, hopingif it was stone it would pop out.
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Quote:
Originally Posted by PhantomRider50 View Post
tj, I do my own oil changes and brakes etc., the car is do for an oil change this weekend, so while I am at it, I guess I will pull the tires and take a look at the rear pads for wear.
If it only happens when you apply the brakes, then I agree with the others, it's something in the pads/rotors, and not the ABS/traction control.

I've gotten rocks trapped between rotor and backing plate. Stuff like that can be a pain to inspect for. You just about need to pull the rotor. I think your plan to pull some tires and inspect is the right call.

As tj noted, if you have a bad caliper, you could find one rotor with the pad on one side worn down to metal making the noise. The cause could be as simple as no lube left on the slide pins.

HTH.

Doug

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Quote:
Originally Posted by PhantomRider50 View Post
tj, I do my own oil changes and brakes etc., the car is do for an oil change this weekend, so while I am at it, I guess I will pull the tires and take a look at the rear pads for wear. I might even call and see if our local O'Rileys does resurfacing of the rotors and may just go ahead and throw new pads on it as well.

ICUBB, I thought that as well at first, but not so sure now, that's why I found the sound went away in reverse, hopingif it was stone it would pop out.


I own a 2014 Impala 2LTZ, purchased new.

The 9th generation Impalas (and 8th generation starting with model year 2012) came new with a specially treated rotor surface (the name escapes me and is an unusual name).

In essence, the rotor surface is specially treated to a certain depth of the metal, which improves wear characteristics and prevents quick surface rusting. ďTurningĒ or machining the rotor destroys the treatment area of the rotorís surface.

I suspect one or more brake pads are sticking and have caused one or more rotors to warp. The rotation of the warped rotor causes the sticking brake pad to make the noise you are hearing.
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Fwiw, I just changed rear pads on a '16 LT Limited recently due to dried/seized guide/slide pins on the lr. Top pin on that side took some "persuasion" to remove. All 4 rear pins got anti-seize compound and new pads going back together.
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post #11 of (permalink) Old 08-14-2019
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Here is information about the finishing process for OEM brake rotors by GM: https://media.gm.com/media/us/en/gm/.../1130_fnc.html
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post #12 of (permalink) Old 08-15-2019
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Could be some rust caught in between. I just replaced the pad guides and cleaned/sanded/greased the guide pins on mine, and they function extremely better, like new.

Yours probably isn't old enough, and this is not of your original problem, but pushing new fluid and bleeding the system is underrated.
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Grinding noise when stoping from the front wheels

I purchased my 2014 (9th gen) LT in Jan 4, 2017 and immediately left NY for FL for the winter months. The car was a "Certified PreOwned" with new tires and brakes at 29,000K (so no grinding). I stopped at the dealer on 9-6-2018 as there was a grinding sound coming from the front brakes. I was right, new rotors & pads (warranty) at 41,000K after only 12,000 miles! I stopped again on 5-9-2019 (50,700K), grinding noise from the front brakes, they said they couldn't hear anything, they must be deaf! Now at 56,000K you can really hear the grinding sound, of course the warranty has expired and I am stuck having to go for the fourth set of rotors & pads in less than 60,000k. I am certainly not going to the dealer, I will try my luck with one of the independents (now past the age where I could do it myself). This is on top of water in the trunk, they replaced the RR Taillight assembly under warranty in FL, on another occasion they replaced (under warranty) the RR fender liner after it came off during a snowstorm, then on another occasion they replaced a sensor that controls the lane change warning light and finally on 7-19-2019 the RR lug nut stud was found to be cross threaded, undoubtedly caused during previous service by Chevrolet! That only cost me $120.00 and that was cheap because the tech was able to save the threads ($10.00 for a new lug nut)o/w I would have to pay for a new stud plus labor(very expensive)!! Since most of our driving is highway the rotors should last to at least 80 to 90K...sad..not a happy Impala owner!
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post #14 of (permalink) Old 08-16-2019 Thread Starter
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Decided to go to the Stealership since they sent me a decent coupon for oil change, tire rotation and inspection. They said brakes and rotors looked good and their Master Mechanic said the noise was coming from a dirty or sticking caliper guide pin just like a lot of you have mentioned, he said it happens quite a bit with them. Then they proceeded to tell me they cold take the front caliper off and clean and re-grease the guide pins for $165.00 plus tax, OMG, they already had the wheel off to rotate the tires, I said, ummmm, no thanks, I will do myself this weekend.
So I will post back after doing this and let ya know if that was the issue.
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post #15 of (permalink) Old 08-17-2019
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I had a 2015 2lt before trading for my new 2019 premier

I went 117,000 on the original brakes and still had 30% left on them. (I even drove for uber for a short while so they were used a lot)

However Iím a car wash guru. At least 3 times a week I go thru and almost daily in winter.

My rotors after 4 years of owning the car didnít even have rust on them.

Iím sure this was a contributing factor of the brakes working so well and so long. Nothing on the car had any rust on it, not even the exhaust. When I traded in the car

Just my $0.02.

Iím sure the brakes failing after 12,000 miles has something to do with a faulting something in the caliper or brake lines. Perhaps bleed the brake system completely. There could be air in the brake lines causing issues for u. 12,000 miles is crazy and especially if ur taking long drives thereís no way they should be failing that soon. Something is keeping light brake pressure on ur rotors causing this to go bad.


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