Brake Booster Constantly Running (1 Viewer)

Joined
Jan 23, 2021
Messages
9
Location
ATX
Howdy y'all. I'm a new fresh GX470 owner, bought a 2003 a couple weeks ago. There's a periodic chugging/cycling noise coming from the brake booster/accumulator/reservoir area that happens constantly when the ignition is turned to ON or the vehicle is running. Brakes work fine and there are no warning lights, but the vibration from the pump/motor can be felt through the pedal. I have a video of the noise but I'm still working on figuring out how to attach it here. I've posted this in the general section as I believe these types of assemblies are common across a lot of the Toyota trucks.

The PO says it's been there for the entire time he's owned the vehicle, about 8 years. I've flushed the very dark fluid that was in there but that has changed nothing. Could this have to do with a failed sensor or limit switch of some kind that's telling the motor to run every 5 seconds? Would like to avoid throwing parts at it up front if anyone has any ideas. Thanks!
 
Joined
Jan 11, 2008
Messages
1,011
Location
Seattle
Never seen anything like it. Possibly there's a pump recharging the ABS accumulator? And it's got a leak so the pressure drops pressure sensor kicks on can pre charges the ABS accumulator again just a theory!
 
Joined
Jan 23, 2021
Messages
9
Location
ATX
I think your theory makes sense. I've tried flushing and bleeding the fluid and rebuilding the master cylinder but I think I may have to try a new accumulator.
 

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