What is that buzzing noise that the brakes make for a moment when the pedal is pressed or let up? It sounds like a servo motor or something adjusting. I can hear it in the cab, but not in the engine compartment and it is only when the engine is running. It sounds like it is coming from the footwell.

 

could be the ABS pump or more likely it could be the vacuum pump kicking on. Do you hear any sounds when you press the brake pedal (like a woosh from the booster)? I'm thinking if you have a leak in the booster or a bad check valve in the vacuum lines, the vacuum pump kicks on to build up vaccuum in the booster...

 

Thank you for replying. I’m sure the sound is normal. It’s always been there since new. I just never understood what it actually is. It’s when the brake is pressed, then again when released. It buzzes for just a moment, perhaps a second or so. It sounds electrical.

 

sounds like you are hearing the vacuum pump.

 

Okay thank you very much. I wasn’t aware that it went on and off.