Brake Booster Failure? Diagnosis Help

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TequilaMechanic

TequilaMechanic

Joined
Aug 26, 2023
Threads
8
Messages
128
Location
USA
Hello,

Is this what brake booster failure looks like or does this point to something more minor?

Got the dreaded BRAKE, ABS, VSC lights and audible buzzer on the drive home the other day.

Restarted the car when I got home and all alarms stayed. Restarted the next morning and alarms vanished. Hooked up techstream this morning.

With car off, I pumped brake pedal until its resistance stopped. Took 34 seconds for the pump to cut off, can see brake fluid dropping as pump runs. Pump/motor was as noisy as it has been which buzzes normally (maybe got complacent with noise).

In techstream my error codes are (without active alarms)
C0278 - open or shut circuit in ABS Solenoid Relay Circuit
C1223 - ABS Control System Malfunction
C1251 - Pump motor is locked / open circuit in motor ground
C1340 - Open circuit in center differential lock signal

So it seems like my system is somewhat operation but honestly with two small kids I’m afraid to drive it right now.

IMG_3373.webp


IMG_3365.webp
 
Time to replace or rebuild the brake booster assembly. Don't tempt fate, its failing.
 
So here is a screencap of a screencap I've saved that identifies the thread and page number of the FB contact info
of the guy that rebuilds these...

Screen Shot 2025-12-23 at 12.20.17 PM.webp


The screencap obviously won't have an active link so that appears to be page #2010 in the "What have you done..." thread, post #40,196
and includes his digits - Andy Le is the guy.
 
Theres a lengthy thread on here with a lot of information on the brake booster.

Mine was leaking like crazy and I couldn't really tell where from, though throwing no codes and working correctly. I wanted to rebuild it simply because a new one is $$$$, but after reading everything I opted to replace. In the end, i'm glad I did. A new motor/pump assembly plus the seals and you're not far off from the price of a new one.

In the end, mine was leaking due to a clogged weep hole in the motor (could have been an easy fix) but also seemed to be leaking between the valve body and plastic solenoid housing (not fixable). I'm glad I replaced mine instead of repairing... Worth it alone just for the piece of mind (this is my kid car as well).

Utilize the 15% off sale going on right now before the end of the year when Toyota is apparently going to raise prices and order a new one. Replacement is pretty easy with a helper to press the pedal and click buttons in tech stream.
 
Andy is worth a try, for sure. A nice guy to deal with, and he understands these things.

That said, I went with a brand new unit from Toyota. This is one area I decided not to trust a rebuilt, as my girls drive this thing.

DO NOT (AND I CAN'T REPEAT THIS ENOUGH) THINK YOU CAN DRIVE WITH THESE WARNING LIGHTS AND CODES.

Get it home, if you are lucky, and park it. It's not if, but when, and I promise you, sooner than you would like...... you are going to have a total brake failure.

If you've ever hit the brakes, and it goes all the way to the floor with nothing, you will swear your truck speeds up!!!
 
DuckLN said:
I’m in the same boat with my 2000 lc. My brakes lasted about 6 miles after the constant beep started.
Click to expand...
A couple weeks ago the alarm went off with my wife driving. She was in our neighborhood and just drove it home. I went to move it in the driveway a couple days later and smashed into our garbage cans trying to move it around in the driveway lol It had brakes........but very little.
 
If you’re handy you can rebuild it yourself for under $300, which includes new master cylinder piston/seals and reservoir seals from Toyota, and new electric motor guts or whole motor from the aftermarket. It’s not complicated or voodoo. I wouldn’t do it, though, if you’re seeing leaks from strange places.
 
Bisho said:
If you’re handy you can rebuild it yourself for under $300, which includes new master cylinder piston/seals and reservoir seals from Toyota, and new electric motor guts or whole motor from the aftermarket. It’s not complicated or voodoo. I wouldn’t do it, though, if you’re seeing leaks from strange places.
Click to expand...
Can you elaborate? I would like to know the actual process on this. I’m very handy (as my wife says), but there is a lot of stuff that makes these things very difficult. The ‘accumulator’ for instance.
 
Yup no plans of driving until fixed. Pulled it into the garage, gonna just count myself as super lucky.

Brake booster assembly w/ master cylinder (47050-60043), gasket (44785-60010), and some DOT 3 ordered. Might rebuild my front calipers while I wait for that to come.

Got techstream functional so that’s good news too. Also was able to look up techstream codes in the FSM.

Thanks for the input everyone.
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squidmotion said:
Can you elaborate? I would like to know the actual process on this. I’m very handy (as my wife says), but there is a lot of stuff that makes these things very difficult. The ‘accumulator’ for instance.
Click to expand...
Skidoo

Thread 'Master Cylinder Rebuild - DIY'

Order correct rebuild kit. Part number for 2000 US model w/ ATRAC is 04493-60330
[edit 6/2018 - this part number is correct for all US 100s. Checked with @beno and while online it will only be listed for 2003-2007, its correct for all US 100s.]
Kit is around $50, so a bunch cheaper than ~$1500 Master Cylinder Assembly. Rebuild will not fix everything, but for the price it is worth a shot. Brake fluid, think I used around 2 qts.
Would be a good idea to have FSM, since this is written assuming you have it.
Tools: 10mm flare wrench, 3/8" socket set...
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Dmi

Post in thread 'Brake Failure_uzj100 Power Brake booster repair-'

This - 47070-60010 ABS PUMP BRAKE MASTER CYLINDER BOOSTER MOTOR 4RUNNER REPAIR KIT | eBay - https://www.ebay.com/itm/144028085078 - is legit.
Arrived with DHL in 4 days from UK Florida. Total with shipping was $160. Came with brushes - didn't use them, see pics for reason. Seems to be balanced. One bearing - noname, one good of a quality.
Finished assembly, putting the preload spring back in place was a not fun of a task. But all worked out great. If someone is doing this - pay attention to clearances.
I also got some stainless steel (I know) M5 hardware (the bolts has to be 6mm...
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Reactions: GTV
The booster ASSY w/Master, is hands-down the best way to go. Care for properly. Most can last 25 years more or less.

I only uses Toyota brake fluid. Which cares fore seal, in ways Toyota engineered for.
 
2001LC said:
The booster ASSY w/Master, is hands-down the best way to go. Care for properly. Most can last 25 years more or less.

I only uses Toyota brake fluid. Which cares fore seal, in ways Toyota engineered for.
Click to expand...
X2 On these more complex Toyota brake systems you definitely want to use Toyota brake fluid. If this was a Camry or Corolla it might not matter as much.
 
A little off topic but... On the last day of my Death Valley 8 day run (life changing) i noticed a noise that appears to be associated with the brake booster / master cylinder. Kind of a buzzing vibration that modulates with brake pedal pressure and then disappears. Is this the beginning of the dreaded booster / MC failure?
 
Nardulli said:
A little off topic but... On the last day of my Death Valley 8 day run (life changing) i noticed a noise that appears to be associated with the brake booster / master cylinder. Kind of a buzzing vibration that modulates with brake pedal pressure and then disappears. Is this the beginning of the dreaded booster / MC failure?
Click to expand...
Most likely. Is you brake fluid dark? Do you know when it was last replace?
 
Mines been audible buzzing/noise (NOT the seagull screeching noise) for as long as I’ve had it (nearly 3 years/17kmiles). I’ve been diligent with brake fluid replacement with Toyota fluid but doubt it’s been fed Toyota fluid for its whole life.
 
The brake booster assembly, does get louder with age. It's either booster motor and or pump. That said:

The accumulator (silver or goldish cylinder). Must not touch the metal bracket/band/cage or any of it's 3 rubber bumpers, that encircles it. We'll get a vibration sound if it does.

Accumulator.webp
 
Aracobuilt said:
Most likely. Is you brake fluid dark? Do you know when it was last replace?
Click to expand...
It is the one thing that I neglected when I bought the rig last summer. I went thru the thing bumper to bumper but somehow ignored the brake fluid. I've got the FSM so I'll just do a rebuild and call it good enough for who it's for.
 
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