HydraBoost Brake Assembly

[BlackWorksInc]

So as you guys know, I had to replace my brake booster assembly with a new one and I was able to keep the old unit. I decided when I had some freetime to tear apart the unit and figure out what possible methods someone could use to figure out how to diagnose a potentionally faulty unit.

Tools Required:
~12mm Ratchet & socket
~Philips Head Screw Driver
~5mm Allen Key or Allen Head Socket
~Needle Nose Pliers
~Pick or hoose (to pull snap ring out)


There are three philips head machine screws that hold the tank onto the unit, then just pull it off.

Next you need to hold this ring down and pop the snap ring out, once you do that, just pull the master cylinder piston assembly straight out of the master cylinder.


Now remove these 4 screws that hold the power and ground wires to the acumulator pump. Then remove the high pressure brake fluid line and the low pressure line from the accumulator assembly.


After you've done that, there are four 5mm allen head screws that hold the acumulator pump and bracket assembly onto the main body of the assembly. remove these and pull the unit off. It should look something like the following.


After you've got the acumulator pump assembly off, there are six 12mm head bolts that hold the ABS Module to the master cylinder. Remove these and be careful with the aluminum/rubber sandwhich gasket when you pull them apart.


This is as far as I decided to tear down the unit as any further would not be cost effective to replace individually. A few ideas that came to mind on possible testing methods, still working them out, but basically as you can see its made up of three main components; the acumulator assembly, master cylinder, and ABS module.

I will most likely update the instructions some later, I just wrote this up real quickly. I basically followed what the FSM says to do.

 

[BlackWorksInc]

I apologize in advance as I had not noticed until now that the Tacoma, FJ Cruiser, and 4Runner after about 2007 or 2008 seem to utilize an updated Hydraboost unit that has a different connector layout than the one I have shown here. I have not had the opportunity to take on out to tear down yet, so the process will be similar but not exactly to the one pictured. I will try to add the .pdf for the updated unit teardown instructions.

 

[Rattlecanpaint]

How much was THAT? Also, Toyota lets you take something like that part and replace individual pieces inside it?

 

[BlackWorksInc]

I think it was around $1700 or online from what I found. I believe we charged the warranty company something like $2300 (dealer pricing) when we did mine.

Technically Toyota does provide information on how to tear the unit down and replace components, but they want the unit replaced as a whole. That being said you can buy parts individually and tear the unit down as shown.

 

[Albush1]

Hello, thanks for all the info regarding the rebuild kit. I ordered and tried to install the new piston in my master cylinder on my 2004 4Runner but I sadly tore the super thin nylon ring that is on top of one of the o-ring seals while trying to install it. I've rebuilt several other types of cylinders with o-rings with never an issue, but this nylon o-ring cover seal/sleeve is so darn thin I can only imagine damaging the new kit I get. Is there a trick to installing the plunger/piston with the nylon seal? Also, did you lube yours with brake fluid or something else? Thanks, Adam

 

[Hawaiian Hillbilly]

need part info purchase links please

hi guys and gals! my wifes 03 runner v8 have a bad booster pump. I tore it all apart and have the pump and accumulator apart from the reservoir. I took the pump cover off and the armatures looks like the culprit. the pump was filthy and full of dust. so if at all possible could you direct me to the place to buy individual pieces of the pump assembly internals please? thank you in advance! aloha from hawaii

 

[BlackWorksInc]

hi guys and gals! my wifes 03 runner v8 have a bad booster pump. I tore it all apart and have the pump and accumulator apart from the reservoir. I took the pump cover off and the armatures looks like the culprit. the pump was filthy and full of dust. so if at all possible could you direct me to the place to buy individual pieces of the pump assembly internals please? thank you in advance! aloha from hawaii

Honestly I don't know of any rebuild kits for these and Toyota doesn't really let you get much more than one or two major sub-assemblies last I checked...

You could try Partsouq.com and see if they sell individual components, but I wouldn't hold my breath on it.

 

[Hawaiian Hillbilly]

many thanks to this forum!

Honestly I don't know of any rebuild kits for these and Toyota doesn't really let you get much more than one or two major sub-assemblies last I checked...

You could try Partsouq.com and see if they sell individual components, but I wouldn't hold my breath on it.

Aloha bud! I tore the pump apart and reconditioned the brushes and armatures cleaned out the gunk from over 200k miles inside the pump.....and VIOLA! SHE IS ALIVE! Thank you for your posts and threads! One of the brushes was jammed stuck inside the pump. So I made the necessary adjustments (freeing up the stuck brush and filing the edges to allow free travel with the spring) and tested it and was pleased. Looking at the brushes it should have a lot more life left. Saved myself a lot of money in the process. much mahalos, HH

 

[ballski00]

I searched around and didn't find a definitive answer: So if my booster pump is priming every few presses of the brake pedal, this would most likely be the culprit? A leak somewhere? Thanks for any help

 

[m85476585]

I searched around and didn't find a definitive answer: So if my booster pump is priming every few presses of the brake pedal, this would most likely be the culprit? A leak somewhere? Thanks for any help

That is probably normal. If it is priming frequently (maybe once a minute or more) when you are not using the brakes then that could indicate a leak.

 

[BlackWorksInc]

I searched around and didn't find a definitive answer: So if my booster pump is priming every few presses of the brake pedal, this would most likely be the culprit? A leak somewhere? Thanks for any help

Every couple to few pumps it will kick in for a few seconds to "top off" pressure. If it's kicking in everytime and running longer than 30 seconds each time, there could be an internal leak of the accumulator circuit.

It will also run up to a minute on start-up normally.

 

[m85476585]

Every couple to few pumps it will kick in for a few seconds to "top off" pressure. If it's kicking in everytime and running longer than 30 seconds each time, there could be an internal leak of the accumulator circuit.

It will also run up to a minute on start-up normally.

On startup it might also run for a while, rest for about 30 seconds, then run for a short time to top off. After that it shouldn't run frequently unless you are using the brakes.

It seems to sense pressure, and using the brakes seems to use up stored pressure. So the harder you press the brakes each pump, the more often it will come on.

 

[ballski00]

ok thanks! the brakes are pretty soft as well so maybe they need to be bled PROPERLY. The PO broke off the front left caliper bleed screw so extracting that should be fun

 

[m85476585]

ok thanks! the brakes are pretty soft as well so maybe they need to be bled PROPERLY. The PO broke off the front left caliper bleed screw so extracting that should be fun

How long have you owned it? A lot of people say the brakes on these are soft compared to other vehicles. Of course it probably wouldn't hurt to put in some fresh fluid if it hasn't been done in a while.

 

[ballski00]

How long have you owned it? A lot of people say the brakes on these are soft compared to other vehicles. Of course it probably wouldn't hurt to put in some fresh fluid if it hasn't been done in a while.

over a year. It's not just that, there is something wrong; maybe bleeding it properly will help.

 

[BlackWorksInc]

ok thanks! the brakes are pretty soft as well so maybe they need to be bled PROPERLY. The PO broke off the front left caliper bleed screw so extracting that should be fun

It does sound like it might have air in the system.

But the pedals on these 4Runners are "soft" in general.

The difference between soft and spongey being that in a vehicle exhibiting a "Spongey" feeling pedal you'll push down but there's little to no braking application by the end of the travel.

With "Soft" you'll feel a consistent application force that does not become harder/require additional effort until you're basically at the bottom of pedal travel. That's because these vehicle have very good assistive force so unlike regular vacuum boosters where the pedal stiffens as you press down, the pedal pressure is extremely consistent in these hydraulically assisted vehicles.

You can actually feel when the brakes grab after getting used to it, despite the "soft" pedal.

 

[ballski00]

It does sound like it might have air in the system.

But the pedals on these 4Runners are "soft" in general.

The difference between soft and spongey being that in a vehicle exhibiting a "Spongey" feeling pedal you'll push down but there's little to no braking application by the end of the travel.

With "Soft" you'll feel a consistent application force that does not become harder/require additional effort until you're basically at the bottom of pedal travel. That's because these vehicle have very good assistive force so unlike regular vacuum boosters where the pedal stiffens as you press down, the pedal pressure is extremely consistent in these hydraulically assisted vehicles.

You can actually feel when the brakes grab after getting used to it, despite the "soft" pedal.

by your definition, mine are spongey. then, when I push hard enough, the brakes seem to lock up a bit with ABS maybe kicking in

 

[m85476585]

by your definition, mine are spongey. then, when I push hard enough, the brakes seem to lock up a bit with ABS maybe kicking in

Could also be bad pad compound. For example hard aftermarket pads plus the soft pedal feel could make for a bad braking experience. But if it's changed over the past year then bleeding seems like a good place to start.

 

[ballski00]

Could also be bad pad compound. For example hard aftermarket pads plus the soft pedal feel could make for a bad braking experience. But if it's changed over the past year then bleeding seems like a good place to start.

it has not really changed over the past year. Before I knew the proper bleed procedure, I tried to bleed to brakes and couldn't ever get all the air out of the rears.

 

[hkollie1]

My 2003 has had the soft and spongey issue, Dealer quoted me $ 2700 part...found a new unit for $1900 online, went with an EBAY unit that has a 1 warranty for $755...with a $200 core fefund = $555

Dealer installed the Ebay unit for $300

reading this I am efinitely gonna send my unit back in for the $200, considered keeping it, and monkeying with it myself....seems like the jury is still out on how to make them work again?