Can anyone help a fellow Hummer owner out?!

[BIGSTUF]

I own a 2008 Hummer H3 Alpha and have recently noticed a strange noise, almost like a humming sound, coming from the engine compartment when I apply the brakes. Not sure if this is a normal noise that I have just picked out, or if this is a new problem that needs to be repaired / replaced. The item is located next to the power brakes reservoir...a "canister." Can anyone help me out in identifying the mysterious canister, and let me know if it is supposed to be making a noise when the brakes are applied. Thanks in advance!

 

[3rdH3]

Instead of vacuum boost, the H3's have an electric motor to boost hydraulic pressure. I hear mine sometimes upon startup if it has been sitting for a while. It is also used to boost pressure in emergency braking. With the ignition on and the engine off, pump your brakes several times to to see if the same noise you are hearing when driving. I normally can't hear mine with the engine running. I have a 10 Alpha. The cannister in your photo is the Power Brake Booster Pump Fluid Accumulator.

 

[LagunaH1]

I know this might be hard to describe but how loud is the humming sound? If it's loud enough to record, maybe record it on video an post here?

 

[f5moab]

that canister is an accumulator that stores pressurized fluid for the braking system. The humming is probably the electric motor use to boost the brake pressure. Most vehicles in this class use a vacuum boost system, the H3 uses electric boost system. (Nice for when you are towed back, all you need is the ignition on to keep braking.)

 

[5gn-h3t]

How long have you had the H3? The brake controller can make some wild noises. Freaked me out at first.

 

[BIGSTUF]

Thanks to everyone for the info. Let's just say it's the same hum as described as when starting the vehicle, only it occurs every time I apply the brakes. As far as how loud it is, it is definitely loud enough to record. I will get an audio clip of it when I get home. If it's electrical, shouldn't there be a fuse to go with it? If so, anybody know which one? Had it a year now.

 

[LagunaH1]

Looking forward to the recording :cheers:

 

[BIGSTUF]

Sorry it took so long to get this audio clip up and running...fighting with YouTube. Anyways, make sure your speakers are turned up and have a listen. Any and all opinions and recomendations are welcomed....hope it's nothing serious!

[video=youtube;4Hqljz6LeSU]http://www.youtube.com/watch?v=4Hqljz6LeSU[/video]

 

[alrock]

All I can hear is the dentist's drill :wink:

 

[BIGSTUF]

alrock, that's a good way to explain it! I should have thought of that in the first description, in stead of a "hum"

 

[3rdH3]

That sounds kinda like it's the booster pump but I don't think activating that often is normal. I hope some more folks chime in to help you out.

 

[BIGSTUF]

Thanks 3rdH3, I hope someone does too I know it's coming from the booster pump because I can put my hand on it and feel the thing vibrate when it kicks in. The reason it's doing it so often in the audio clip is because I'm pressing the brakes in the vehicle. Every time I press the brake pedal, it makes that sound.

 

[LagunaH1]

I think F5 already commented on this, but the brake booster in the H3 is electric so it's expected that it activates every time you step on the brakes. I can't tell whether the amount of noise is normal.

 

[f5moab]

From here, it sounds pretty normal. One way to test the system is to listen to the sounds made.

If you have someone step on the brakes and there is a hissing noise, that steadily increases as the apply pressure to the brake pedal increases, it is normal. Also, if you apply the brakes firmly and then pull your foot off immediately allowing for a fast brake release there should be a clunk (sometimes sounds like a clatter or click), it is operating normally.

If you have a gauge that can measure the force applied to the pedal I can look up the specs and supply them.