Eh Another ABS/Brake Booster replacement question - Is it the booster or accumulator?

[hickuptruck]

Another one of these brake booster/ABS threads. Trust me I searched!

I purchased an '02 LX back in November with 172k miles on it. It had the buzzing noise from the MC when I test drove it. But about a week after, I got the ABS Brake Trac dashboard lights go off with the alarm. The brakes still felt solid. I pulled the codes off Techstream and they were the usual C1252 C1256 etc. However, I drove about 40-50 miles and the alarm disappeared along with the dash lights.

However, I still get the slight buzzer noise somewhere from the MC that lasts 2-3 seconds after I use the brakes two or 3 times. I have searched and this indicates that the electric motor in the ABS accumulator/booster is going. I would like to fix this ASAP as brakes are extra important, especially with a vehicle with ATRAC. However, I don't want to plop down $2500 for the whole OEM unit when the car was only $5k. I would be ok having a vehicle without ABS but since ATRAC relies on it, I'd like to get the system back. Right now the ATRAC seems to work fine and ABS too.

Which leads me to this: am I replacing the booster (just the black piece) or do i need to replace the booster and the accumulator (Black piece and metal cylinder with yellow warning stickers)? I have good brake pressure, it is just that I have the electric buzzing noise after 2-3 brake pumps.

Here are pictures for what i am referring to:

Booster - getting off a rebuilt unit for $300-400

or Do i Need this entire unit: rebuilt booster and accumulator? This is harder to find rebuilt - the 2 pieces

 

[100 TD]

There are 3 parts there, motor, pump, accumulator. Electric motor turns/runs (may sound like buzzing), turns the pump. The pump pushes fluid into the accumulator against the high pressure diaphragm, when it gets up to pressure, the pressure switch turns off the motor(and stops pumping). It sits there pressurized waiting for you to use the fluid from the accumulator for your braking needs. When you use a few pumps worth of fluid, the pressure drops, pressure switch activates and turns the motor on again, pumping up the accumulator.
The reason your alarm comes on could be a failing motor, a failing pump, and sometimes a failed accumulator. The pump(motor and pump) need to pressurize the accumulator to specified pressure in a certain time, if it doesn't, then it will alarm, each time you use the brakes, it reduces the pressure and the motor starts if necessary. If you master cylinder, pump, accumulator etc has an internal leak, and the pressure slowly drops, pump runs again. AFAIK, mostly the commutator and brushes fail on the motor, I don't know the life of the pump, if it's a standard gear pup it should go a long time if it isn't contaminated. You need to work out what you need, generally the motor, and while you're there, change the master cylinder piston. Whether you have these or other problems, I don't know. YMMV

 

[Beazer76]

Any update on your fix here? I came across this one today...debating on replacing mine. OEM Brake Booster Pump for Land Cruiser 100 Series, 4Runner, Tundra

I have the dash alarm and light go off on occasion (only two times), but never when I'm driving it. It last went off when my mother drove the vehicle while my wife and i were out of town. She parked it till I got home several days later. I happen to get a video of it. I'll see if I can post it. - The brakes felt fine when I pushed on them.

 

[hickuptruck]

Bought a junkyard one for $280. No more lights or alarm but the booster is loud and goes on every 2 brake pedal pushes.

 

[aharlan001]

So I've replaced the pump/motor but still getting the alarm and Techstream pump/accumulator codes so is it a leak in the master cylinder or accumulator? Pedal is firm no braking issues besides the deafening alarm.