Question on 1999 LX470 Hydraulic Brake Booster

[ffl3883]

Hello,

I always notice a buzz sound for about 10 sec long from the accumulator whenever after I press brake pedal 3-4 times. Could any Guru explain whats going on ? I am just wondering if the buzz sound and frequency is normal. How do I know if my hydraulic brake booster is failing besides DTC?

Regards

Fliu

 

[vipergrhd]

I will try to explain, the buzzing is your ABS pump building pressure in your accumulator every time you press the brakes pressure drops inside the accumulator thus the pump comes on. The pump can run as long as 10-15 seconds if the accumulator pressure is low and needs to build up the pressure back where the factory sets it, if you hear a lot of pump running even with just a few pumps of the brake the accumulator could be leaking.

 

[heywood]

Mine did this only in really cold weather for years until this year. It did it in all weather conditions and for up to 45 min when it was really cold (triggered the brake and ABS lights/ buzzer after about 5 min). Replaced the entire booster assembly (not cheap), but it seems to have fixed the issue and I like the idea of having reliable brakes.

 

[ffl3883]

Mine did this only in really cold weather for years until this year. It did it in all weather conditions and for up to 45 min when it was really cold (triggered the brake and ABS lights/ buzzer after about 5 min). Replaced the entire booster assembly (not cheap), but it seems to have fixed the issue and I like the idea of having reliable brakes.

Thanks for your reply. After replacing the entire assembly, do you still hear any buzz sound in the accumulator after pressing brake several times ?

 

[heywood]

I haven't tried to drain the accumulator by pressing the brake a bunch of times, but in normal use, I haven't heard the buzzing sound at all.