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Brake noise heard when braking

Tiny
SOLARFLARE1975
  • MEMBER
  • 2008 HUMMER H2
  • V8
  • 4WD
  • AUTOMATIC
  • 2,000 MILES
Hi,
I have a brand new 2008 Hummer H2. When I apply the brakes, I'm hear a brake squeal. I thought at first that this was coming from one of the wheels. The dealership that I purchased the truck from said it should go away with a little driving. After driving 2000 miles, the noise is still there. I have now found that the noise is not coming from any of the wheels, but rather from under the hood.
You can sit in Park, and apply the brake pedal, and recreate this brake squeal, without moving the vehicle. If you apply the brake pedal hard and fast it will not make the noise. If you apply the brake pedal slowly (like in city traffic), it will make the squeal. The noise is almost the same as a regular brake squeal caused from a brake pad.
Do you have any idea what this may be? I know that the new 2008 Hummers no longer use a vacuum system for the brakes anymore.
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Thursday, January 15th, 2009 AT 3:23 PM

11 Replies

Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
They use a Hydra-Boost system (run off P/S pump) If so you may have a bad belt or tensioner if you can pump the pedal and make a squeak, it may be the drive belt if it will do it when the vehicle is sitting still.

Can you please shoot a quick video with your phone so we can hear the noise? That would be great. You can upload it here with your response.
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Thursday, January 15th, 2009 AT 9:23 PM
Tiny
SOLARFLARE1975
  • MEMBER
  • 4 POSTS
I have the newer style electric motor/accumulator brake booster system. I have not actually looked physically at it as of yet.
I have been noticing a drive belt squeak early in the morning when the truck is first started up. But goes away once it is driven.
I will open the hood and see if I can take a picture as well.
My dealership is over 3 hours away. So that is why I can't take it right in.
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Friday, January 16th, 2009 AT 6:54 AM
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Are you sure the noise is coming from the wheels? Depending on how much the electric booster motor draws it could load down the alt and cause it if the belt is already squeeking in the morning
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Friday, January 16th, 2009 AT 7:22 AM
Tiny
SOLARFLARE1975
  • MEMBER
  • 4 POSTS
I'm 99% sure that it is not coming from the wheels. I can reproduce the same noise with the truck in park, and applying the brake slowly.
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Friday, January 16th, 2009 AT 7:37 AM
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Have someone sit in it and duplicate the noise so that you can hunt it down
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Friday, January 16th, 2009 AT 8:36 AM
Tiny
SOLARFLARE1975
  • MEMBER
  • 4 POSTS
I just stopped into a GM dealership about an hour ago. I know the service manager there. He got in my truck and heard the high pitch squeal noise. We opened the hood and he could hear the noise. He felt around. He said it is the accumulator motor making the noise, and he could feel a pretty good vibration from it. I can only get one pump out of the brakes, before the acculmulator comes on again. So in other words, I hit the brake, it squeals, hit brake again, no squeal, hit it one more time, it squeals again. So there is something definitely wrong.
The service manager said it's probably normal for it to do that. I looked at him cross eyed. No other 08's that I tried had this noise. It's also getting more persistent. While stopped at a light and keeping foot on the brake, the accumulator would come on again for a few seconds and shut off.
Do you have any ideas? I'm assuming that the accumulator is not holding the correct pressure, causing the motor to run more often. I'm still not sure what the noise is. But I assume it is the motor.
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Friday, January 16th, 2009 AT 3:15 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Has this issue ever been resolved?
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Wednesday, April 1st, 2020 AT 8:12 PM
Tiny
MCIOCI
  • MEMBER
  • 3 POSTS
I have the same issue on my 2008 Hummer. I changed the accumulator but that did not help at all. If anyone has any clue pls respond.
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Thursday, April 29th, 2021 AT 9:58 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
Hi,

Are there any lights on such as ABS, traction control, or others?

Have you had the CAN system scanned for codes? CAN stands for controller area network, Basically, all the different modules are tied together via a few wires. If you scan the can system, it should identify any codes stored regardless of what module it's stored in.

Take a look at this video. it shows how it's done.

https://youtu.be/InIlnsjOVFA

Let me know if there are any other issues other than a noise.

Joe
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Friday, April 30th, 2021 AT 5:29 PM
Tiny
MCIOCI
  • MEMBER
  • 3 POSTS
No lights on. There are no codes. It only happens the first time I use my brakes in morning. If I am driving on for a long time it will not do it. I can shut off truck, start it again in an hour and it will do it again. I think it has something to do with ABS but cannot figure out what is causing it.
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Monday, May 3rd, 2021 AT 12:09 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,179 POSTS
What I would suggest is this: Before driving it, have a live data scan tool connected and watch the wheel speed sensors signals. Are they equal? There could be dirt, corrosion, or a loose tone ring at one of the wheels causing one of the wheel speeds to be wrong.

If that happens, it will cause the ABS to actuate simply because it thinks it is in a skid.

Let me know if that is something you can do.

Take care,

Joe
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Monday, May 3rd, 2021 AT 6:03 PM

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