It's going to be at leas a couple of weeks or more to get parts and the time off work to get mine fixed, I'm still debating with myself if I'm just going to replace the entire assembly or the motor/pump/accumulator portion which I can get for a little more than $700.

I also saw you can get the master cylinder without the motor/pump/accumulator portion for around $1180 which would save about $200 over the entire assembly if Marten just needs that part.

47025-60081 Genuine Toyota Brake Master Cylinder Sub-Assembly)

Even a little cheaper here.

Toyota 2003-2005 Toyota 4Runner Brake Master Cylinder 47025-60081 | Toyota Parts

Thanks Au and Sam for your efforts

I am running out of time. Sick of my inability to analyze the situation properly I already ordered the new hydro booster unit. It's the full unit, to get this unit out of the failure equation.
I should have the unit soon and I'll let you know what difference it makes.

Martin

Hi Au,

Rock hard pedal meaning you had no brake booster at all.
You have a leak on the pressure side
In lack of a technical diagram of the unit it is unknown where the leakage might be located
1)hydraulic 3-cylinder pump/check valve being part of the pump so that pressurized fluid cannot flow backward,
2) accumulator super low on gas (cannot store much energy meaning any leakage is amplified by a weak accumulator) ,
3) downstream a potential leak on the pressure side toward the master cylinder.

Unfortunately I don't have any better information.,

Can you do these quick tests and see how well your system responds once pressurized?

test1:
Key in ignition position
press the brake pedal 3 times as a start.... after how many brake actions
does the motor come on. After 1, 2 or 3 pushes?
For instance after every second push you'll hear the motor. So you push 2 times...brake motor.... push 2 times...brake motor.

(my T4R has the 1-2 pattern. Every second pedal action the motor comes on)


test2
Key in ignition position
Push the brake pedal more often... say 10 times.
Does that trigger the low pressure alarm (all 4 dash lights plus alarm sound)?

(I can trigger the alarm after 6-8 pedal actions)

These tests don't tell you how leaky your pressure side is because these leaks are relatively slow - you said it takes overnight for all pressure to leak out.

But it can tell you probably about the basic condition of the brake health.

I am sure you will get rid of your symptoms with a new unit.
Martin

I just ordered the complete assembly for mine as well, not taking a chance with not replacing it all, don't have the time for my vehicle to be down if just replacing some parts of it doesn't solve the issue.

I was going to order from Ourisman since it was less initially ...BUT after shipping and them charging taxes was added as well it was $100 more than ordering it from ToyotaPartsDeal, who was less on shipping and didn't charge me $96 in taxes!!


I should have it somewhere between May 2 and May 7, then I need to find the time to install it.

Martin,

I tried both already...BUT I'm have trouble even hearing the electric motor running, I have been noticing over the last year or so the motor kicking in more often, running longer than it should and it was nosier than is was in the past, I'm pretty sure the brushes are worn out and barely making contact and running must more slowly than it used too, hence why it takes 3 to 4 minutes to build up the pressure to stop the alarm and get the lights to go off.

All that said, it is 20 years old so I think I got more life out of it than I would of from any other manufacturer!

Good decision.

My approach: Why do it the right way when I can do it my way.

You went as far as you could so a good decision. If you are not too burned out by this, I would like to see your failure analysis. Maybe tear the block down and look at internal seals.

Yes, analysis might come at a later stage. First I need to get this truck going.

I am coming back to my earlier point criticizing the 'modern' cars and my tendency to drive a car before OBD...
The complexity and entanglement of modern cars with electronics paired with a shop manual vacuum lacking detailed documentation makes it almost impossible to understand systems like the brakes. Unless we are doing private reverse engineering the only chance is to throw parts at the problem.

For instance bleeding of the brakes calipers... you can ask 3 people and you might get three different recipes and none of the recipes might explain why these steps are done this way.... I can see the 'beliefs' rather than proper understanding what is happening and this comes by a lack of understanding of the hydro brake unit.

I have to admit I need to recover after this episode. Please keep fingers crossed that the new hydro booster unit might bring some change.

Best, Martin

I also broke down and finally purchased a Bi-directional scanner that is capable of bleeding the ABS system, as well as all a OEM scanner can do, I did my homework first before buying it, it's highly recommended by "The Car Care Nut" Toyota specialist that's on Youtube.

I'm old as dirt and have been doing mechanic work for well over 55 years, it was my profession for many years before I went into home building 30 years ago and I can rebuild and fix anything blindfolded that was built before computers took control of everything, it's finally time I took control of those computers and the only way I can do that is with a scanner that gives me that ability.

I still do work on all of my family's and many friends' vehicles so I have been needing this scanner for quite sometime now!!

If I could give more than one "like", I would.

I started my shade tree / junk yard career during the OBD2 era so that's what I sort of know. Rarely does a DTC tell you what part is broken. Usually, there is a check list of symptoms to match up and parts to try. Usually, it's the simplest issue that causes the code but I admit to shotgunning parts until the code resolves. I also admit to failing due to complexity beyond my understanding and well beyond my crappy scanner. We saw all of this in this thread.

Werm's problem was a lot more complex than mine. My hydro-boost codes were C1223 which we already know as ABS malfunction and C1252 which is hydro-boost pump motor malfunction. This combined with obvious motor noise and no loss of brake power made for easy diagnosis and fix. The hard part was going as cheap as possible. I cross referenced pump and accumulator on ebay of all places, found a GS300 at the JY, tested the motor with 12V, paid $65 with no warranty, and was back in business in three hours. I will never say I know what I am doing but I will say I have patience and access to many junk yards.

Speaking of old school, I just got a 1989 Jeep running after sitting for 5 years. Minimal electronic controls with pesky solenoids. It had a carb, coil and distributor spark system, and mechanical fuel pump. There was not much to understand and it felt like I could learn the systems in no time at all. I get why people love old cars and want to go back. (The Jeep needed a couple of relays. If it were mine, I would have replaced the carb and some other items.)

Thanks Au,
I was looking into this scanner D7 Xtool. Sound fabulous.
Do you think this tool would have helped to analyze my ABS codes in a better way and we would find a conclusion faster?

Best, Martin

Martin,

Very likely it could, at the very least it could help somewhat, the one I bought is the Xtool D8S which I found for around $100 more than the D7, normally it's about $200 more, but I was going to get the D7 until I saw the CarCareNut had compared them both and the D8 was a little better, but they both can do almost the same tasks, he said the D7 was the best DIY scanner and close to a professional level scanner for a third of the cost, the D8 he said was as good as most all the professional scanners other than the $5000 Snap-on scanner, and both are as fast or faster than the Toyota OEM scanner, I really need to also get a OEM Toyota shop manual because this scanner can do all the Toyota scanner can do but for some of the tests you need to follow steps in the manual.

With a Bi-directional scanner you can test various components individually, for an example, say your driver's window stops working, you can send a signal directly to the motor bypassing the switch, if the window responds, then you know it's the switch that is faulty, basically you should be able to test various components, computers, etc. I'm also having issues with my AC so I'm hopely the scanner will help me pinpoint the part that has failed.

Hi Au,

brake motor running for 3-4 minutes? Wow.... that is way too long.
motor and accumulator are in question.
tests: No engine is running for these tests. Only key in ignition, hood open and window down. You will hear the brake motor loud and clear, push the brake a couple of times and the el. motor starts and stops. It is very obvious and audible.
I asked the question a few times during the thread: how often does the motor start during normal braking... barely any answers, no data. The best I could understand was... Every third hit the motor typically starts, I hear the brake motor every second time at the moment.
I think people simply don't know. And I understand, why listening to that motor when the brakes work.

I got not a single answer from anyone if people can replicate this: Engine off, Key in ignition , Hit the brake for instance 10-15 times hard. Does the alarm come on?

"20 years old so I think I got more life out of it"
I have 3 old Mercedes, 32-54 years old with their original brakes...they all work so much better than the T4R breaks ... unfortunately.

Martin