Landcruiser HDJ100R 07/2002 Hydraulic brake booster/ABS control unit problems.

[gjd123]

Hello Good mud folk,

I want to pick the brain of people on here that have more knowledge than me in this area,
A while back I had an unexpected brake failure, I was 2hrs from home, but got back safely on what little brakes I had. The following week I removed the entire unit , from that I removed the electric motor, sent it off to get rewound and replaced the Accumulator, took a but of mucking around with bleeding without scan tool but the buzzer stopped, warning lights went out and I had brakes ..... for a day. The problems have returned. The accumulator kicks in every 10 seconds for two seconds, now, some important info - if I disconnect the four wiring harness to the hydraulic brake/ABS control module unit in the engine bay, so there are no electrical signals coming from/to the brake booster unit, there are two ABS relays that click/activate every 10 seconds for two seconds from the relay box on other side of engine bay, so could all these problems stem from the ABS ECU under the drivers side dash perhaps??

 

[gjd123]

Hello Good mud folk,

I want to pick the brain of people on here that have more knowledge than me in this area,
A while back I had an unexpected brake failure, I was 2hrs from home, but got back safely on what little brakes I had. The following week I removed the entire unit , from that I removed the electric motor, sent it off to get rewound and replaced the Accumulator, took a but of mucking around with bleeding without scan tool but the buzzer stopped, warning lights went out and I had brakes ..... for a day. The problems have returned. The accumulator kicks in every 10 seconds for two seconds, now, some important info - if I disconnect the four wiring harness to the hydraulic brake/ABS control module unit in the engine bay, so there are no electrical signals coming from/to the brake booster unit, there are two ABS relays that click/activate every 10 seconds for two seconds from the relay box on other side of engine bay, so could all these problems stem from the ABS ECU under the drivers side dash perhaps??

 

[2001LC]

First; I'd don't replace parts of the brake master assy (the whole deal), except in test vehicle for research. It can be done, but may result in failure, of the most import vehicle control safety device we have other than steering. Loose either can be deadly.

Second: The booster motor is designed to run often but short duration. If coming on, every few minutes, without brake pedal being depressed. You most likely have air in system and or a leak.

We want to make sure you good brake fluid and no air in system. I only use Toyota brake fluid. Which in USA, we can't get the good stuff. Good stuff being what factory put in. But I still only use Toyota bottles, it make a difference IMHO.

You, need to make sure no air in system. The test for this, is:
IG Key Off.
Pump peddle 40 times. (This evacuates booster accumulator, dump fluid back in reservoir)
Top fluid to max line in reservoir. (This is how we set level)
Turn IG key to on. (Booster motor starts)
Time how long booster motor runs to charge system (pressurize accumulator). Spec is 30 to 40 seconds. Over 40 seconds rebleed.

Note:
Make sure the battery has at least 12.4volts. The time to charge system, will take longer, the lower the voltage. 12.7V is ideal! Higher voltage results in lower time to charge.

Saying you "mucking around with bleeding"? Is lacking in detail. I've no idea if you did properly. Many mess this up!

Inspect brake master assy for leak.
Inspect brake hard lines for leaks.
Inspect flexible lines for swelling, bubbles and or leak.
Inspect calipers for leak.

Additional issues and inspection:
If at anytime, you heard the dying segall sound and see bubbles coming up front of reservoir, at same time. The brake master non replaceable seal, is bad. The master is scrap metal.

Reading this link, may help you diagnose.

Brakes ...... Overdue write-up.

First and foremost: Brakes should only be worked by those, with high level of mechanical abilities and experienced with brake systems. With the age of all 100 series today, in our aging fleet. Any issue, with brake master assembly. IMHO, best and safest course of action. Have the whole brake...

forum.ih8mud.com

 

[gjd123]

Just a follow up on my problems with my brake booster/ abs unit on my Landcruiser HDJ100R just recently I removed the entire unit to look it over one last time for faults before replacing the ENTIRE assembly which goes for nearly $4000 AUD.
The guy I sent the DC pump motor to rewind, had sent back the newly rewound motor, but also a used pump, anyway, I swapped out the pump, then reinstalled the brake unit assembly, bled the brakes and BAM! The Audible alarm stopped and the ABS and warning lights went off and I have brakes again! So the small pump that sits between the pump motor and accumulator can and does fail, which will in turn overwork the motor attached to it causing that to fail too.
So if anyone has an accumulator kicking in every 10 seconds (for 2 seconds) then look at replacing your pump (and motor). Sounds so simple I know but out of everyone that I spoke to, and some that are highly technical in the field of brake and ABS systems, not 1 person said that the actual pump cold be the problem, They suspected just about every other component.
Hopefully, this information can help someone, cause there are still plenty of vehicles with these brake unit/ ABS assemblies in them

 

[2001LC]

You said you removed the motor and rebuilt. But didn't mention testing it first or inspecting internally. How did you know motor was dead, and what was wrong with it?

A pump can fail, but not something I see happen. We'd likely see a very stained reservoir, indicating very bad old fluid run for a long time. Which could then wear on pumps vanes. But they just tend to weaken, not fail. Many parts in a master can fail. We touch one and then another fails. It's why we replace the whole deal.

Failed pumps, usually leak out weep hole, between pump and motor. They still pump fluid and produce pressure, but weak. So it takes long to get up to pressure.

There is a little key between pump and motor, that must be set incorrectly.

Notice fork at end of motors shaft.

Your reservoir looks good (no staining). Assuming you did not clean it. Which is condition of old fluid and reservoir, are clues I use. Bad fluid, damages master seals. Good fluid, master seals usually good as is pump.

Interesting. Appears you have a single rear brake line. USA 100 series, use one rear in 98-99, then in 2000, went to two to rear. This was with addition of VSC in 2000.