Poll on total brake failure in 100 series

[2001LC]

25-60041 Is brake master only. It is W/O brake booster assy. If it is, all you can find in USA, then get it. Then you'll need to purchase booster assy separately.
50-60041 Is the Booster assy W/brake master. The whole deal, and is best buy. Save labor and dollars on parts.
The -60041 is earl version w/ "A" type (flat blade wire housing block) pressure sensor. It was only in the July 1999 thru Aug 2000. In fact, many 2000 LC&LX, starting in Jan 2000 thru Aug. Have the B type pressure sensor. "B" type pressure sensor, was used from ~Jan 2000- 2007

Many Dealerships, will not ship brake masters and show N/A. So make sure and call, to see if they have. Serra Toyota is one of the few that will ship.

"A" type sensor (flat blade). I'm holding between finger & thumb.

Don't buy from outside USA. You'll pay way to much. First more for part, then ~72% more ($ shipping, 15% duties, then 25% tariffs and 2.5 to 10% fees).

 

[ScotyDosentKnow]

I replaced my failed brake master/booster with a new OEM unit.

Filled the reservoir with fluid and pumped 40 times with the key off. When I turn key on the motor comes on but doesn’t run. It cycles on and off. Not sure what to do here, tried 5 or 6 times now.

When I pump the pedal there is some pressure but seems to go away after about 10 pumps.

Please help

 

[2001LC]

You must flush and bleed from all 4 caliper bleeders.

 

[Mchodl]

The warning is lasting longer, tepid temps (50-60f) seems to impact it the most. Almost 5 minutes of pump cycling to fully pressurize. Motor, accumulator and master cylinder rebuilt in 2021. At least the whole booster assembly is a third of the price it was in 2021

 

[2001LC]

The warning is lasting longer, tepid temps (50-60f) seems to impact it the most. Almost 5 minutes of pump cycling to fully pressurize. Motor, accumulator and master cylinder rebuilt in 2021. At least the whole booster assembly is a third of the price it was in 2021

View attachment 4071206

Pressure loss.

Failure of master within two years of booster side rebuild, is common. It's one reason, why I, no longer rebuild master. I replace the whole master ASSY. Safer and saves on long terms cost.

A few spot to check:

1. May hear a squeal and see bubbles in front area of reservoir. If non replaceable master seal is failing.
2. Look very close for even the slightest small wet stain. Along bottom of ABS unit (black box side of master)

This ABS unit leak at front. Leak may be out of sight on bottom or back.

 

[LandCruiser105]

Here's a question - for those who have bit the bullet and bought a whole new brake assembly, did your booster pump noise become much quieter? Could you hear the new unit pumping whilst sitting in the cabin with the engine running?

For example a car I've been looking at has a booster pump you can easily hear inside the cabin with the engine running. Yet it doesn't sound like it is damaged though and pumps within 35 seconds so passes that FSM test. However another car is very hard to hear in similar circumstances - same ~35 sec refill performance and same sort of sound! But much quieter. (Both same engine (1FZFE) on standard exhausts.)

I am wondering if booster pump noise levels are also a factor in determining booster health / likely longevity in addition to all the other data points. @LC2001, you must have changed a fair few of these by now. Is that an observation you or others have seen?

 

[2001LC]

Here's a question - for those who have bit the bullet and bought a whole new brake assembly, did your booster pump noise become much quieter? Could you hear the new unit pumping whilst sitting in the cabin with the engine running?

For example a car I've been looking at has a booster pump you can easily hear inside the cabin with the engine running. Yet it doesn't sound like it is damaged though and pumps within 35 seconds so passes that FSM test. However another car is very hard to hear in similar circumstances - same ~35 sec refill performance and same sort of sound! But much quieter. (Both same engine (1FZFE) on standard exhausts.)

I am wondering if booster pump noise levels are also a factor in determining booster health / likely longevity in addition to all the other data points. @LC2001, you must have changed a fair few of these by now. Is that an observation you or others have seen?

With new booster ASSY w/master (the whole brake master assy). They do not produce enough sound to hear, sitting in cabin, windows up, hood closed, engine running. Even standing at fender hood open, it's hard to hear with engine running. It's why we do the booster run time test, engine off. Old booster ASSY, do tend to be louder. But, I give very little weight in grading a master, to being louder. The exception is screeching sound with bubbles seen in frt of reservoir. A sound we hear clearly, engine running.

One thing to check, that can make a lot of noise:

I do find the metal band bent. From shipping damage.

 

[thex2]

Thank you for all of the info the members of this thread have contributed. I'm at 144,500 miles on my 07' and I'll be replacing the Brake Booster/Master Assembly here shortly. No failure yet. Just curious, it sounds like I'll need to do this again at 300k miles, correct? The Toyota replacement doesn't offer any improvement on the original parts?

 

[LandCruiser105]

Well, if you replace it and then keep the brake fluid very clean with regular flushes, AND make sure you don't every top it up incorrectly (only topped to the MAX line after 40+ pumps of the brake pedal, with ignition OFF), then you ought to have a setup that lasts much longer than another ~150,000. That would be the short version of a long thread! I have over 24 years and 200,000 miles on mine - still seems good. The two major points of failure seem to be letting the fluid age too much, and overfilling which then drips onto the motor electric supply and corrodes that - resulting in $$ failure.

 

[Aracobuilt]

Well, if you replace it and then keep the brake fluid very clean with regular flushes, AND make sure you don't every top it up incorrectly (only topped to the MAX line after 40+ pumps of the brake pedal, with ignition OFF), then you ought to have a setup that lasts much longer than another ~150,000. That would be the short version of a long thread! I have over 24 years and 200,000 miles on mine - still seems good. The two major points of failure seem to be letting the fluid age too much, and overfilling which then drips onto the motor electric supply and corrodes that - resulting in $$ failure.

Facts! Clean brake fluid is crucial. I neglected this and my brake booster started acting up. I thought I was going to have to replace it, instead I replaced the fluid. The issue went away for a few weeks and came back. I flushed the fluid again and I have been good for 6 months. I am getting ready to flush the fluid again. An important note, use Toyota brake fluid, especially on these more complex brake boosters. It has additives that prolongs the life of the seals.

 

[2001LC]

I'd not replace brake master assy. Unless I've a reason to do so.

First being no brakes. Which only happens if no pressure in system.

1. Failure of booster motor to run.
2. No fluid in master.
3. Booster motor running excessively long, with squeal sound and bubble seen in front of reservoir. Master seal failure.
4. Leak seen between master & ABS unit (black box on side of master). Leak just gets worst and alarms will ensue; motor will burn up.

Otherwise, I grade them, on a scale of 1 to 10. 10 is new:

1. Brake control wire screws/leads corrosion/rust. Heavily -3, medium -2, light -1.
2. Reservoir staining. Heavily -3, medium -2, light -1. Note: If fluid looks good and no staining. I'd consider just replacing booster side, if clues warrant it.
3. Condition of fluid, without staining. Very dark -2, Dark -1, Clear 0.
4. Pumps of pedal with resistance, until accumulator evacuated. 40 -3, 35 -2, 30 -1, 25 -0. Note: If no staining and fluid good. Above 35 pumps. I'd consider just replacing booster side (accumulator), if clues warrant it.
5. Time to charge accumulator, w/12.5V minimum, fresh Toyota brake fluid and system properly bled, no leak. Over; 40 seconds -3, 36 -2, 34 -1, 30 -0. Note: If no staining and fluid good. Above 38 pumps. I'd consider just replacing booster side.
6. Age. 25 yr -2, 15 -1, 9 -0.9, 8 -0.8, 7 -0.7 and so on.

Things to consider when thinking about replacing, just a component.

• If we replace any part of booster side. This results, in additional pressure in master system. We very often see, within two years. One or more, none replaceable seal(s) fail, within master or ABS unit. We then must R&R master. This result in added labor.
• If buying new Toyota parts. All components' that make up the whole, bought separately. Cost more than the whole.
• Availability. Today there is one of our masters out of production. It's the 2000, with type A pressure sensor. So, we can't buy from Toyota. I've found and bought the last one, "known" to be in a Toyota warehouse or Dealerships globally. Toyota shows it, as out of production. One day, all will go out of production. IMHO: Not likely anytime soon on the 01-07. We may get down to just one P/N, which today there are ~3 for 01-07.

First 9 post, of this threads has a ton of info. That may help with understanding our electrical Brake Master:

Thread 'Brakes ...... Overdue write-up.'

Nov 1, 2020

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 master assembly, replaced with new. If you have to ask question, on "how to", your not qualified to work on the master.

My hope is below link will give better understanding as to what we can do to reduce brake failure and what to watch for. The info is from my experiences and my thinking, as to what...

• 2001LC

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[2002LX]

Does anyone have literature beyond FSM with step-by-step detail on how the master, booster assembly, abs functions? I’ve read almost the entirety of 2001LC’s thread on brakes and searched the web but haven’t seen anything fully outlining series of actions that happens starting with depressing the brake pedal.

From what I can make out, our unit functions similar to a power steering assisted hydraulic braking system. Difference is our booster pump draws from the brake master itself to pressurize the accumulator. Then, does the accumulator “assist” in multiplying pedal force or does it directly pressurize the brake circuits that opens when depressing the brake pedal? Or is it both?

1. Rear circuit - Directly pressurized by accumulator? Fluid flowing continuously when bleeding rear brakes with pedal depressed makes it seem like this is the case for the rears

2. Front circuit - Indirectly pressurized? Here the accumulator pressurizing rear circuit “assists” pedal force to the front?

Lastly, how does the fluid in the accumulator “drain” back into the master? Is the excess fluid pushed from the accumulator into the circuits flowing back into the reservoir when the brake pistons draw into the calipers after releasing the brakes?

 

[uHu]

Does anyone have literature beyond FSM with step-by-step detail on how the master, booster assembly, abs functions? I’ve read almost the entirety of 2001LC’s thread on brakes and searched the web but haven’t seen anything fully outlining series of actions that happens starting with depressing the brake pedal.

From what I can make out, our unit functions similar to a power steering assisted hydraulic braking system. Difference is our booster pump draws from the brake master itself to pressurize the accumulator. Then, does the accumulator “assist” in multiplying pedal force or does it directly pressurize the brake circuits that opens when depressing the brake pedal? Or is it both?

1. Rear circuit - Directly pressurized by accumulator? Fluid flowing continuously when bleeding rear brakes with pedal depressed makes it seem like this is the case for the rears

2. Front circuit - Indirectly pressurized? Here the accumulator pressurizing rear circuit “assists” pedal force to the front?

Lastly, how does the fluid in the accumulator “drain” back into the master? Is the excess fluid pushed from the accumulator into the circuits flowing back into the reservoir when the brake pistons draw into the calipers after releasing the brakes?

The "New Car Features" section in the FSM explains the function pretty well. Attached.
You're right. Without accumulator pressure you have no rear brakes. The fronts are actuated by the smaller, inner piston; if there is no booster pressure available.

 

[2001LC]

Does anyone have literature beyond FSM with step-by-step detail on how the master, booster assembly, abs functions? I’ve read almost the entirety of 2001LC’s thread on brakes and searched the web but haven’t seen anything fully outlining series of actions that happens starting with depressing the brake pedal.

From what I can make out, our unit functions similar to a power steering assisted hydraulic braking system. Difference is our booster pump draws from the brake master itself to pressurize the accumulator. Then, does the accumulator “assist” in multiplying pedal force or does it directly pressurize the brake circuits that opens when depressing the brake pedal? Or is it both?

1. Rear circuit - Directly pressurized by accumulator? Fluid flowing continuously when bleeding rear brakes with pedal depressed makes it seem like this is the case for the rears

2. Front circuit - Indirectly pressurized? Here the accumulator pressurizing rear circuit “assists” pedal force to the front?

Lastly, how does the fluid in the accumulator “drain” back into the master? Is the excess fluid pushed from the accumulator into the circuits flowing back into the reservoir when the brake pistons draw into the calipers after releasing the brakes?

In addition to @uHu response.

For more than what is in FSM on brake system. One needs to go into Toyota school manuals. Even then, it's more general overview.

 

[2002LX]

@uHu Thanks, that’s super! Turns out the answer more often than not resides in the

 

[Nardulli]

I've noticed that on startup there is a new 'noise' that appears to be coming from the general area of the booster / master. It sounds like an electric motor noise. It starts at cold start and runs for about 10 - 15 seconds. From time to time, while maneuvering - as in a parking lot - I will hear it come on briefly. Brakes are functioning properly. No warning lights. Is this the beginning?

 

[uHu]

I've noticed that on startup there is a new 'noise' that appears to be coming from the general area of the booster / master. It sounds like an electric motor noise. It starts at cold start and runs for about 10 - 15 seconds. From time to time, while maneuvering - as in a parking lot - I will hear it come on briefly. Brakes are functioning properly. No warning lights. Is this the beginning?

Depends. The booster pump motor running like that is normal. If it is just the normal sound of an electric motor, you're ok. Might be that you just haven't listened for it before. If, otoh, the sound is like a suffering motor, or a pump screeching, you might be close to disaster.

 

[Nardulli]

Depends. The booster pump motor running like that is normal. If it is just the normal sound of an electric motor, you're ok. Might be that you just haven't listened for it before. If, otoh, the sound is like a suffering motor, or a pump screeching, you might be close to disaster.

Thanks. It doesn't sound as if it is laboring - it is just that it is a new noise.

 

[Mchodl]

Pressure loss.

Failure of master within two years of booster side rebuild, is common. It's one reason, why I, no longer rebuild master. I replace the whole master ASSY. Safer and saves on long terms cost.

A few spot to check:

1. May hear a squeal and see bubbles in front area of reservoir. If non replaceable master seal is failing.
2. Look very close for even the slightest small wet stain. Along bottom of ABS unit (black box side of master)

This ABS unit leak at front. Leak may be out of sight on bottom or back.
View attachment 4071240

Occasional squeal coming from master. No leaks noted. Swapped new unit.