Brake Booster Motor cycling on and off repeatedly

[murphthelab]

Trying to resolve ABS/Brake/Audible-alarm issue. Did my research, read the posts.

1) Diagnosed booster motor failed. Rebuilt and re-installed booster motor.
2) Tried to clear ABS alarm and properly complete "Bleed Hydraulic Brake Booster" procedure.
3) I pump the brake 40+ times, turn on ignition and listen to brake booster motor. I can hear motor engage. But it only runs for a few seconds. Then turns off. Then engages again after maybe 5 to 10 seconds. Turns off again after just a few seconds. Rinse and repeat.

I can hear and feel the ABS relay(s) engaging according to the above repeating cycle. Bottom line, the accumulator pressurization process is not completing properly.

What is likely cause? Perhaps ABS controller (black box on side of MC assembly) is responsible?
I certainly would prefer to avoid a wholesale Assembly replacement. Starts to cost near the value of the whole rig.

 

[JunkCrzr89]

Sounds like the accumulator may have failed and needs replaced. The general consensus is that if you replace the motor then the accumulator should be replaced as well, which I'm sure is why Toyota sells them together in a kit.

 

[murphthelab]

Yes, I've seen this reported as well. I chose the motor repair because of course this is far less $s than buying a motor / accumulator-pump assembly kit. And the motor does now work. But...

Now that I'm here, I just don't recall hearing about this repeating on-off cycle that I'm experiencing. But it makes logical sense, I guess. If either the accumulator pump or the accumulator chamber starts to fail, the duty cycle of the motor will increase, eventually depleting the motor life.

I can procure the accumulator by itself (canister) for few hundred $$. But the pump portion seems to require purchase with a new motor and is definitely more $$s.

Any consensus on whether the problem typically resides in the accumulator itself? Or is the pump a more likely culprit?

 

[hoser]

Go with the accumulator since it is easy to change. If that doesn't work out for you, I have a used known working pump you can have (~180k).

 

[nissanh]

Motor runs to maintain the pressure because the accumulator has gotten weaker (not keeping the required pressure). First replace the accumulator before your motor wears out.

I've been studying these types of ABS pumps and helping my Cousin to fix is 01 Montero full size truck. He heard his motor running most of the time and thought system had air, so he bled it. same.. motor continues to run.. and then ended wearing the motor.

He then rebuild the motor and still the same thing. After searching many many videos and threads all over the world, we concluded it is the accumulator that failed (All Mitsubishi's have this issue, thankfully not all toyotas!)


See this guy's videos:

 

[murphthelab]

Can I avoid removing the entire brake booster assembly to change out the accumulator with a new one?
FSM only shows accumulator removal after whole assembly removed from vehicle.

I'm guessing:
1) depressurize using 40+ brake pedal pushes with ignition off
2) find suitable tool (e.g., oil filter band wrench) to turn accumulator counterclockwise.
3) screw on new accumulator
4) hope and pray

Can anyone confirm?

 

[JunkCrzr89]

Yes, you can remove it without pulling the entire booster assembly. There is an o-ring (part # 9030113014) that does not come with a new accumulator but needs to be replaced when you install the new one. You might want to buy a new spring, too (part # 9050116160) and consider replacing the control wire (8963930100).

 

[murphthelab]

Thanks JunkCrzr89. Very helpful.

I will say however, the last thing I want to do is replace that control wire. That opens up a whole new project. The existing screws will undoubtedly require drilling and extraction. A real mess. As long as I can keep them intact, I'd rather leave them be.

 

[nissanh]

Make sure to release the pressure by pressing the paddle 40 times with ignition OFF.

 

[murphthelab]

Saga continues...
Ordered, received, installed Accumulator. Check.
Toyota told me it was the only one left in the country (Atlanta warehouse). Purchased at internet price. There are others on Ebay (more $$s) and from UAE (long time to ship).

Fingers crossed as I re-attempted the booster initiation process. The booster motor started by cycling again, but gladly switched over to continuous after a bit. The booster motor did not stop after 30 to 40 seconds, so I repeated the 40-pumps and ignition-on cycle a few more times. No luck. I feel like I'm missing something regarding the booster bleed.

Most generic brake guidance for modern ABS systems indicates that if you take apart the ABS/Accumulator system, you use a bleeder valve on the booster system before bleeding the four wheels. The LC has no bleeder valve on the booster assembly that I'm aware of. However, there is this statement in the FSM:

"If the hydraulic brake booster has been disassembled, disconnect the brake line from the hydraulic brake booster or if the reservoir becomes empty, bleed the hydraulic brake booster."

When do I disconnect the brake line? When I'm undergoing the booster bleed? Won't that spray brake fluid?
Just a bit frustrated. Can't get the brake system to consume the newly added brake fluid. Stays pegged at "max". Should I just move right to bleeding the brakes at the four wheels?

 

[nissanh]

Try bleeding all 4 wheels. I posted a video done by an eastern European. He has a prado brake booster repair. His helper turned the ignition on and the press the brake and hold, while he loosen all 4 lines on the master. Once fluid starts squirting out on all 4, he quickly starts closing each. Once all closed, his helper takes the foot off the paddle and turns ignition off. Then he suggests to bleed on all 4 wheels same way but one wheel at a time

 

[murphthelab]

Bled all four wheels. Twice.
I have now replaced the booster motor and the accumulator.
I definitely have more braking action than I did when the ABS light/alarm came on and brakes failed initially.

BUT...

• Alarm and lights still on.
• Braking power still well below 50%
• Booster motor cycles on and off every few seconds, repeatedly.
• Booster motor stops when I pump on the brakes (maybe that's expected).

Not sure what to do next.
Am I at the point where I should secure an ABS code reader and see if I get something other than a generic ABS code?

 

[murphthelab]

Any votes from the i8 cognoscenti?
Code reader? Rip & replace motor + pump?

 

[azngarage]

Hi
I have the same issue. Did you ever figure out the problem?

 

[PrescottTrails]

Any votes from the i8 cognoscenti?
Code reader? Rip & replace motor + pump?

I have the very same scenario. (It's almost as if I wrote your thread Anyway, did you finally resolve the on/off cycling of the booster pump? If so, what's the secret? Thx.

 

[PrescottTrails]

Hi
I have the same issue. Did you ever figure out the problem?

Did you ever find a solution for this?

 

[WhiteTrash85]

Did you ever find a solution for this?

Did anyone figure this out? I have the same issue. I’m assuming replacing the entire brake master cylinder unit &pump is the solution, but I would like to hear if there has been success for this specific issue. (All lights, alarm, brake failure, and ABS motor cycles on and off)

 

[Malleus]

Did anyone figure this out? I have the same issue. I’m assuming replacing the entire brake master cylinder unit &pump is the solution, but I would like to hear if there has been success for this specific issue. (All lights, alarm, brake failure, and ABS motor cycles on and off)

Have you tried using Techstream? What codes do you have?

 

[WhiteTrash85]

Have you tried using Techstream? What codes do you have?

I don't have techstream (probably time to invest in it) but I was able to pull the ABS codes with blue driver and got these:
C0210
C1223
C1246
which I think are pointing to an ABS wheel speed sensor.

I let the truck idle for 5 minutes the other morning while I was working on pulling codes. The dash lights and alarms all went away and the brakes pressurized. I had brakes again. I am still going to do more diagnostics but this leads me to believe maybe the master cyl/booster isn't dead. Strange that a wheel speed sensor would leave me with no brakes and a depressurized system though. I'm guessing the booster ins't as healthy as it needs to be. I will try the 40 pedal press and time the motor again.

 

[azngarage]

Did anyone figure this out? I have the same issue. I’m assuming replacing the entire brake master cylinder unit &pump is the solution, but I would like to hear if there has been success for this specific issue. (All lights, alarm, brake failure, and ABS motor cycles on and off)

I end up replace the entire brake master cylinder assembly.