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Brake Booster Buzzing


DanW
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My power brake booster makes this annoying buzzing sound....doesn't do it all the time. Its sort of a faint, high pitch buzzing or squealing sound. Engine doesn't have to be running. I'm sure its coming from the booster.

Testing per the factory manual, it doesn't seem to be leaking. Has made this sounds since I bought the car over a year ago and doesn't seem to be getting any worse, its just annoying.

Any ideas? Its just starting to get on my nerves...

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My power brake booster makes this annoying buzzing sound....doesn't do it all the time. Its sort of a faint, high pitch buzzing or squealing sound. Engine doesn't have to be running. I'm sure its coming from the booster.

Testing per the factory manual, it doesn't seem to be leaking. Has made this sounds since I bought the car over a year ago and doesn't seem to be getting any worse, its just annoying.

Any ideas? Its just starting to get on my nerves...

Oh and by the way, it only happens when you depress the brake pedal, and only sometimes (maybe every 3rd or 4th time)

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My power brake booster makes this annoying buzzing sound....doesn't do it all the time. Its sort of a faint, high pitch buzzing or squealing sound. Engine doesn't have to be running. I'm sure its coming from the booster.

Testing per the factory manual, it doesn't seem to be leaking. Has made this sounds since I bought the car over a year ago and doesn't seem to be getting any worse, its just annoying.

Any ideas? Its just starting to get on my nerves...

had the same problem with an 02 gs 300 it was bad had to be replaced lucky it was still under warranty

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My power brake booster makes this annoying buzzing sound....doesn't do it all the time. Its sort of a faint, high pitch buzzing or squealing sound. Engine doesn't have to be running. I'm sure its coming from the booster.

Testing per the factory manual, it doesn't seem to be leaking. Has made this sounds since I bought the car over a year ago and doesn't seem to be getting any worse, its just annoying.

Any ideas? Its just starting to get on my nerves...

had the same problem with an 02 gs 300 it was bad had to be replaced lucky it was still under warranty

When you say it was 'bad' what does that mean? Did it or will it eventually fail?

Thanks for the info.

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My power brake booster makes this annoying buzzing sound....doesn't do it all the time. Its sort of a faint, high pitch buzzing or squealing sound. Engine doesn't have to be running. I'm sure its coming from the booster.

Testing per the factory manual, it doesn't seem to be leaking. Has made this sounds since I bought the car over a year ago and doesn't seem to be getting any worse, its just annoying.

Any ideas? Its just starting to get on my nerves...

Oh and by the way, it only happens when you depress the brake pedal, and only sometimes (maybe every 3rd or 4th time)

I would suspect a very small tear in the diaphragm, causing a woodwind type reed vibration sound. Your booster holds a vacuum for a few minutes so when you shut down you can still hear it. Probably needs replacing, or just live with it, itll get worse after time, possibly to a dangerous level, pedal will sink to floor with all boost gone.

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The vacuum booster has an apply valve, and a release valve. The apply valve sources atmospheric air on the passenger compartment side of the firewall, at least if it's like most cars. You may hear an audible sound from the small filter that is normally part of the valve as air moves in to provide the assist.

If the booster holds vacuum for any length of time the valves are ok and the diaphragm is ok. If the diaphragm fails the pedal will become very hard and hardly move at all. You can test this for yourself by pressing the pedal several times with the engine off. As the vacuum is depleted only pedal pressure will operate the brakes, and the pedal will be very near the top, and far less effective. It won't go to the floor when the booster fails. Pedal stroke is determined by the hydraulic system, and being a tandem master cylinder it won't depress all the way even if one half of the hydraulic system fails completely - a very rare occurence in itself.

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The vacuum booster has an apply valve, and a release valve. The apply valve sources atmospheric air on the passenger compartment side of the firewall, at least if it's like most cars. You may hear an audible sound from the small filter that is normally part of the valve as air moves in to provide the assist.

If the booster holds vacuum for any length of time the valves are ok and the diaphragm is ok. If the diaphragm fails the pedal will become very hard and hardly move at all. You can test this for yourself by pressing the pedal several times with the engine off. As the vacuum is depleted only pedal pressure will operate the brakes, and the pedal will be very near the top, and far less effective. It won't go to the floor when the booster fails. Pedal stroke is determined by the hydraulic system, and being a tandem master cylinder it won't depress all the way even if one half of the hydraulic system fails completely - a very rare occurence in itself.

Thanks for the replies. It almost sounds like I shouldn't worry about it. Its not that loud, so turning on the radio or even the AC on medium or high 'fixes' it.

I'm not losing any brake fluid, and the booster itself pumps up solid with the engine not running....doens't leak....it's just annoying.

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My power brake booster makes this annoying buzzing sound....doesn't do it all the time. Its sort of a faint, high pitch buzzing or squealing sound. Engine doesn't have to be running. I'm sure its coming from the booster.

Testing per the factory manual, it doesn't seem to be leaking. Has made this sounds since I bought the car over a year ago and doesn't seem to be getting any worse, its just annoying.

Any ideas? Its just starting to get on my nerves...

had the same problem with an 02 gs 300 it was bad had to be replaced lucky it was still under warranty

When you say it was 'bad' what does that mean? Did it or will it eventually fail?

Thanks for the info.

yes it failed

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  • 3 weeks later...

Hi guys,

I have the same problem - after I had noise I changed the whole master cylinder and bleeded the system. it happened that the squeling noise disappeared but there was regular noise and I started to loose breaks, I have bleeded it 3 times but it doesn't help - still regular pppppppppppiiiiiippppp noise and loose break pedal from time to time.

Please advise what is wrong?

I have been told that the system needs to be reset by the computer to put the valves in correct manner of opening. Is this correct?

Thanks in advance for your help

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