My best guess is that you need to clear the code/s, you should be able to clear the code/s by disconnecting the battery for 30 second or longer, once you reconnect the battery your power windows and sunroof will not work properly until you reinitialize them, look in your owners manual for how to do that.

Hi Auseeker,

I did disconnect the battery for some while but the beeping and dash warning chistmas tree lights are not going away.
I can hear the booster motor run constantly during this event.

What does it mean?

The motor is running or making a sound but is unable to produce any pressure on the system. The brake system pressure is not reached and therefore the beeping and warning lights?

What else is causing the warning light?

What does the constant running of the booster motor mean?

Any help analyzing the sysyem is good.

Martin

If the ABS/booster motor is running constantly it's usually either the accumulator and or ABS/booster pump is bad and not building up pressure.

Many people just replace the entire master cylinder/booster assembly just to make sure everything is working, instead of throwing different parts at it until they get it working.

Accumulator part number is 47950-30010 ....link...

2001-2005 Toyota Motor & Pump 47950-30010 | Toyota Parts

Pump and accumulator assembly part number is 47070-30060 ....link...

2003-2009 Toyota 4Runner Power Brake Booster 47070-30060 | Toyota Parts

Complete master cylinder/booster assembly part number is 47050-60010 ...link...

1998-2003 Toyota Actuator Assembly 47050-60010 | Toyota Parts

Thanks Auseeker

For my understanding: The warning light goes on if the minimum pressure is not there.

The pressure is not built up
A) if the pump is not working properly and
B) if the accumulator cannot store the pressurizes oil?

The pump i can understand but the accumulator not so well.
If the accumulator is leaking at the piston seal (if this is a piston accumulator) the pressure will still the built up but cannot be stored because the 'sping effect' of the compressed nitrogen gas is lost.

Is this happening?
....But then the pressure would be reached... just not stored which would possibly lead to a fast on/off cycle of the pump.

Okay whatever this is I already bought a remanufactured unit (Pump and accumulator.

I could install that unit (pump/accumulator) either directly or I could remove the entire assembly and then swap pump.accumulator on the bench and put the entire unit back into the car.

Is there a preferred way to install?
I guess I need. to bleed the entire system again as would drain the fluid out of the unit anyhow.


Best, Martin

my money is on the motor, its making a sound, that may not mean its working ok. anyway, good you have bought a remanned unit. that should solve the issue.


edit: are you sure the fluid isnt leaking out anywhere?. is the level the same?. the motor, did you try holding it with your hands when it was actuating?. was it hot or warm..vibrated throughout or intermittently?

Hi earthrealm,

The brake system is leak free since I fixed the rear brake line

Swapping motor/pump/accumulator with a reman unit.
I was removing the hydro booster unit today (lots of crawling under the dash, not very difficult but definetely not convenient). Working with brake fluid is always messy.

With the unit on the bench it its relatively easy to swap motor/pump and accumulator.
Then I installed the updated unit back into the car and filled the tank with fluid.
I did not bleed the system yet but wanted to see what happens when I start the engine

So I started the car and the dash was silent! Finally some success.

Okay something must have been causing the problem , either the old motor or the pump or the accumulator.... or a combination of these.

I opened the motor (just 2 allen screws) and to my surprise it looked almost new, there is no reason the motor was failing.

If the motor is good then the problem must be a failing pump or a failing accumulator.

My logic tells me that it must be a failing pump.

I am assuming that the brake alarm ((dash lights with the beeping) goes off if the system does not have enough pressure.
Pressure is built up by the motor and pump action. The accumulator is simply storing pressure and if the accumulator fails pressure cannot be stored.
(unsure what this means in regards to the alarm- does someone know?)

As the motor was tuning and is actually looking really good the problem could be the pressure pump.


The good news: I have no alarm.
Tomorrow I will bleed and test the brakes.


The confusing parts was that I obviously had two brake problems at once
1) the leak in the rear brake circuit which turned on 'Brake!' in the dash and then right after the full alarm went off meaning 2) the brake pump failed.

Is the brake pump prone to failure if the system is low on fluid?
If yes that would explain what happened.: First I ran out of fluid and then the pump failed because there was no fluid?

Martin

I was looking at the removed and obviously failing motor/pump accumulator unit on my bench.

I could easily run the el motor and fluid was squirting out at the pump outlet.
The pump could be a 3 cylinder piston pump but not 100% sure.

My theory so far: the pump was failing and could not deliver the required pressue. This lead to the dashlight not clearing.

Well I still have no proof but I might take the pump apart at some point.

Here is a picture of the motor inside... it looked pristine, like new, see picture.

Martin

Attached Images

 

It could be something as simple as the O-ring that seals the accumulator being bad.

yeah, the motor is in great shape, you can sell it for a couple of bucks on ebay. wish i could get my hands on the motor, my 2nd replacement unit is failing again and its either the motor or piston assy


the 2nd likely culprit is the oring on the piston assy. its a 60 dollar part.


the accumulator rarely goes bad, its just a metal cylinder and an o ring on top. its easy to see/know if the accumulator is leaking, as slight fluid would be seen leaking from the top/connection



anyway great news your brakes are working ok now

Hi earthrealm,

Piston assembly.... you mean the accumulator? Is this a piston accumulator then?
[The accumulator is mounted onto the pump and the pump is holding the motor and the accumulator. ]

The o-ring potentially going bad is the one between pump and accumulator?

I don't see a shrader valve for filling the accumulator with nitrogen...meaning the accumulator is not to be refilled with nitrogen.
if the charge is gone.... it is not reusable.

What is the shut off pressure (pump shut off) of the brake fluid under pressure (accumulator filled) if charged?

Martin

Accumulator again. (I am in the hydraulic business and I know this stuff...at least).
If fluid is leaking through this o-ring... that is just a fluid leak... but the accumulator would still work. ( I had NO leak there at any time).
It would need to leak A LOT for a brake failure.

The more realistic option for an acculuator failure is the loss of nitrogen. I a piston accumulator the piston seals would be leaking and the loss would result in a gradual loss or reduction of pressure storage to a point when fluid pressure cannot be stored at all.

If fluid storage (volume of fluid under pressure) is reduced then then pump has to work mpre frequently to make up for the reduced storage.
If no pressure can be stored any more then the pump would run at all times.... which would be deadly.
I don't know how the Tooyota controls work for the hydro brakes but I guess the alarm would go off as soon as the motor runs too often?

I am still trying to analyze why my brakes failed or what exactly failed...

Best, Martin

in a normal brake system, you gotta depress the brake pedal for 2 or 3 times...before the pump kicks in to top up the system. in a failing system. just onetime depression of the brake pedal and the pump kick in. the pump isnt designed to run all the time or too frequently, hence if the failing pressure causes the pump to run too frequently, the pump may burn out, or the 40amps fuse powering the pump fails. then when u open the pumps, you will see debris inside the assy. your pump was squeaky clean, so your failure must have been something else in the assy. the piston assy is connected directly to the brake pedal...and has an oring which traps pressure, if this fails..the system cant maintain pressure and subsequently causes the pump to overwork and fail. replacing the pump in this scenario will just be a bandaid...as the new pump will still fail after a while.


47026-60090 GENUINE OEM TOYOTA PISTON, MASTER CYLINDER 4702660090 | eBay the piston assy looks like this

Your best bet is to buy one of those code readers from amazon, I got one for $30 it’s def worth it. OBD2 scanner

Sounds like a brake line is either broken, worn, or bad. Maybe this is why you had zero fluid in the reservoir, and no brakes. Happened to me too recently. Check your lines before replacing the brake master cylinder. Itll save you

Hi earthrealm

My braking power is not the greatest and I had the same issue (no good braking power) before the incident /brake failure.

Could your note be a hint.

With 'piston' you meant master brake cylinder piston- correct?
This piston in the T4R might just work as any other master brake cylinder? ... I guess.

Sure, if the piston seal of the master brake cyl. is not tight any longer then the brake pedal would drop to the bottom and not find a stop....

I don't know if this problem occurs in my brake.

Again my brakes have been much better in the past and I should find the reason for the weak brakes.
Could be
-air in the fluid? (But I just bled the brakes)
-brake pads bad? (Replaced pads 3 years ago- ceramic pads....)
-calipers bad? (I had rebuilt the calipers also 3 years ago.... the pistons were partially stuck in the calipers)
-master brake cylinder?


Any further hints?

Best, Martin