What is the normal working sound of the brake master cylinder/booster? (1 Viewer)

zhloea

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Hi, I could hear the humming sounds from my brake cylinder/booster from the cab frequently, is this normal?

Below are the cases/timing of my brake cylinder/booster making sound:
1. when I have a long time did not start the truck then I start it and flooring the brake, for example, the truck sits in a garage overnight, I can hear the sound when floor the brake panel and I start the truck the next morning.
2. after hit the brake many times, let's say after keep hitting the brake 5 to 10 times, it starts to humming
3. when I hold my foot on the brake panel for couple mins, for example when I wait for a red light, it will start humming some time.

And the sound not that loud but I can clearly tell when it starts and stop. The brake always working well, just the sound. And it is LC100 2004.

Is this normal? or means there is some issue with the brake cylinder/booster? Thanks!
 
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Mine makes all kinds of whirring noises and humming noises, all of which are normal. There is a motor and a big pump involved. The sounds that are abnormal would be silence or a screeching sound.
 

zhloea

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Mine sounds very close to that one, thanks!
Should do the steps that he outlines where you can time how long it takes to pressurize, sounds like 40 seconds or more may be a concern. In the meantime some preventive maintenance like a brake fluid flush may help. I just paid Toyota to do mine and I think it was semi affordable, maybe $120 bucks or so. Seemed worth it, they also repaired some damaged bleeders while in there.
 

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