Master Cylinder Rebuild - DIY

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that won't work. I physically cannot install the unit w/ the ABS control module attached. So i need to find a way to convert the MC to non-ABS. But looking at the hydraulic diagrams, I'm not sure it can be done??
That is probably a good place to stop. This sound like, well I only need a 4 cylinder engine and I have a V8 and and a recip saw. You might be able to make a working 4 cyl, but really not worth it.
The brake ecu / valving is doing more than ABS, things like frt/rear proportioning, etc. Folks who have done something like this go back to earlier models without ECU/ABS's.
 
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That is probably a good place to stop. This sound like, well I only need a 4 cylinder engine and I have a V8 and and a recip saw. You might be able to make a working 4 cyl, but really not worth it.
The brake ecu / valving is doing more than ABS, things like frt/rear proportioning, etc. Folks who have done something like this go back to earlier models without ECU/ABS's.
I believe you are correct, Skidoo... i think this can of worms may be more like pandora's box.


Just out of curiosity... you mention "earlier models w/o ECU/ABS" - Do you happen to know of any Toyota electric MC's w/o ABS? That could solve my challenge, if it exists!
 
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Don't know which models they used, but the ones I saw had vacuum boost. Maybe someone on here knows.
You might start a new thread here asking what you are looking for.
 
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great step by step...I am a 2:banana: mechanic at best and I was able to complete this exact job over a year ago...over 20k of miles since and still working well.

This was my alternative to entire replacement when I started getting spongy braking and a pedal that would not return. I also replaced all of the grommets...they looked fine but since I bought them, I did it.

nice work.
Hi! Where did you get the grommet and O-ring set??
 
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You may have a point there - I'm not seeing an easy way of getting them on and off.

My motor doesn't look great, but it also doesn't appear to be the cause of my issues. The brushes and commutator still have some life left, though one of the bearings is nearing its end. I'm thinking a likely culprit of the constant cycling is the o-ring at the accumulator. I will probably end up replacing the motor anyway but will go with an already-refurbished unit.

An update to my post #476:

At this point I've rebuilt the master cylinder, replaced the accumulator o-ring, spring and pipe, cleaned out the motor, and replaced the unit on the vehicle. I bled the system pretty thoroughly using techstream and pedal, and then actuated the VSC solenoids (SRMF & SRMR). Can someone confirm this is correct? I have a very firm pedal.

I'm still getting the same cycling from the pump/motor/accumulator.

Before I order a new pump/motor/accumulator, does anyone have any thoughts on other solutions/troubleshooting steps? Since I'm not getting a soft pedal, I'm wary that the issue is not mechanical but electrical, and that replacing the pump/motor/accumulator won't address whatever it is that's signaling the motor to keep turning on and off. I might be better off replacing the entire assembly but that's way more money.

Would I get a soft pedal if the accumulator wasn't holding pressure? Do the accumulators go bad?
 
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Ordering this kit, as my brake fluid looks gross.

do I need an assistant to bleed the brake system? I dont have many friends, just dogs.
 
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Ordering this kit, as my brake fluid looks gross.

do I need an assistant to bleed the brake system? I dont have many friends, just dogs.
You can bleed the brakes with a vacuum assisted system.... but probably easier just to have someone to help. They don't need to be a licensed driver, any kid who can press the brake pedal over and over should work.
 
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Going to do this in the coming weeks. I can hear the pump coming on at strange times, so hopefully its the MC. If my issue persists may be an abs sensor, but it will feel good to get the MC rebuilt and get fresh fluid in.
 
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I came up with a different way to remove the piston, where I do not think is a chance to score the cylinder.

GaVSLQr.jpeg


I cut across a piece of pipe laying around, cut both ends perpendicularly so that it won't be angled, then drilled 12mm opening on another piece of scrap metal and put the threaded part through it. I gripped with big pliers to stop the threads from moving and then started tightening the bolt on top. With a 60mm piece of pipe and 2mm piece of metal on top you have the right amount of thread to cleanly extract the piston.
 
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I came up with a different way to remove the piston, where I do not think is a chance to score the cylinder.



I cut across a piece of pipe laying around, cut both ends perpendicularly so that it won't be angled, then drilled 12mm opening on another piece of scrap metal and put the threaded part through it. I gripped with big pliers to stop the threads from moving and then started tightening the bolt on top. With a 60mm piece of pipe and 2mm piece of metal on top you have the right amount of thread to cleanly extract the piston.

Great idea! might be a bit overkill, but no denying that it will come out cleaner and smoother than the option I used.
 
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First "double pump" episode happened last week at just under 200k miles. Was going to flush/bleed the fluid and see if that helps (looks ugly), but ordered the master cylinder rebuild kit as well. Hopefully that works.
 
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@YardPig I'm going to post some picture of master seal as you request, in next post.

First let me say; I've never had a leak at master to deal with on a 100 series. What I have dealt with on the Master Assembly of the 100 series is corrosion of control wire that connects between ABS to pump motor, dead booster motor and failed ABS unit. That is in order of issue that I see most often.

When I use to work on GM, Ford, Chrysler, etc. I was rebuilding master cylinder often. They would leak at plunger seals. We could see this fairly easily by looking in foot well around master or something in engine bay on firewall just below master.

I just don't see this on Series 100. I'm not saying the seals of plunger don't fail. Just that I've not had to deal with. IMHO the number one reason the plunger seal failure may be related to brake fluid. Either not flushing fluid as often enough or adding "wrong or bad" fluid that's damaging to components. Toyota did have a recall (2005-07 IIRC) for master seals, but not on the 100 series. It seems the issue was with adding non Toyota fluid causing seals to fail. My money was on the rubber that was used. As any DOT I, II or III should have worked just fine, but didn't.

Keep in mind we are only talking about master assembly herein this thread. But be aware, the parts down stream like caliper piston seal, flexible & hard lines we're seeing fail more and more with age. Inspection is key!

I'll state what I feel is obvious as to which leaks/failed seals in the 100 series need addressing. But first I'll restate something that was just posted in the "Brake failure thread". It is the one part that will fail and with little to no warning, no matter how well we maintain or inspect. It will cause brake failure or at least until all but bottom of peddle travel and then very little braking. This is the Booster motor. The motor has brush that wear out. Interestingly I've found commutator worn-out (dead spots) and bushes still have enough material to last for hundreds if not thousands of hours. I'm seeing this failures around 250K miles. BUT Miles aren't the key to motor life, it's hours of motor run time. City stop and go drive using brakes often vs all HWY miles is obviously going to have motor run more and so failing at lower miles. Other issues can cause motor to run often such as moisture in fluid, air in system (fluid), leak(s), weak accumulator. It's also possible for the ABS to not delivery current to the motor or the resistance wire to go bad. But I'm just seeing motors bad. In any case, if that motor fails, booster pressure is not regained with use and peddle will go to the floor.

I've been replacing motor and cleaning up wires for those that are on a tight budget. But really the best is to just go ahead and replace the accumulator assembly with new in our aging fleet. I found www.partsouq.com has the best deal at $800. It includes motor, pump, accumulator and wire.
Accumulator assembly circled in black
View attachment 1888271

Here is wire corrosion I find in about 30% of all rigs I've inspected. Why...it may be related to overfilling reservoir more than anything else.View attachment 1888303

After I saw this thread I took a look at my booster motor, there is some rust outside the motor, is this something I should concern? (brake works fine)
will that possible the ex-owner had a motor failure and he replaced with a used motor? (because you could see it looks obviously old than other parts)

Other parts of the cylinder/booster look ok, the places around the brake fluid reservoir from top to bottom are bone dry, with no oil mark.
seems the ex-owner changed the radiator host T s, would it possible is splash coolant when those Ts broke?

Screen Shot 2021-05-08 at 2.12.46 AM.png

Screen Shot 2021-05-08 at 2.13.09 AM.png
Screen Shot 2021-05-08 at 2.13.28 AM.png
 
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flintknapper

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After I saw this thread I took a look at my booster motor, there is some rust outside the motor, is this something I should concern? (brake works fine)
will that possible the ex-owner had a motor failure and he replaced with a used motor? (because you could see it looks obviously old than other parts)

Other parts of the cylinder/booster look ok, the places around the brake fluid reservoir from top to bottom are bone dry, with no oil mark.
seems the ex-owner changed the radiator host T s, would it possible is splash coolant when those Ts broke?

The corrosion on the outside motor housing is purely cosmetic and of no real concern. Likely the result of spilled brake fluid or an 'overfill'.

The area of concern is under the two rubber caps where the connecting screws reside. They have a tendency to 'rust' badly which causes resistance, which in turn can effect the electric motor. I would peel those caps back and inspect the screws.

Caps Motor.png

Corrosion1.jpg
 
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The corrosion on the outside motor housing is purely cosmetic and of no real concern. Likely the result of spilled brake fluid or an 'overfill'.

The area of concern is under the two rubber caps where the connecting screws reside. They have a tendency to 'rust' badly which causes resistance, which in turn can effect the electric motor. I would peel those caps back and inspect the screws.

View attachment 2668479
View attachment 2668482

Hey man, I did this check the bolts in the rubber cover and it looks good, but I did that pump timing test twice, I got 50seconds and 52 seconds. what I did is I hit the brake pad 40+ then turn the key on (not start engine), then it starts the pump, no warning sound, the car sit there overnight before I do the test.

So is it bad? or I did the test in the wrong way? If it is bad, will a dealer brake flush help?
 

flintknapper

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Hey man, I did this check the bolts in the rubber cover and it looks good, but I did that pump timing test twice, I got 50seconds and 52 seconds. what I did is I hit the brake pad 40+ then turn the key on (not start engine), then it starts the pump, no warning sound, the car sit there overnight before I do the test.

So is it bad? or I did the test in the wrong way? If it is bad, will a dealer brake flush help?
You did the test just fine. You are a little out of spec for timing, but not alarmingly so IMO. Since aren't getting the warning beep....I would drive it and just check it from time to time. IF the fluid is old then a full 'flush' with new fluid would be good, but I wouldn't expect it to change the test results much (if any) unless you have air in the system.
 
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You did the test just fine. You are a little out of spec for timing, but not alarmingly so IMO. Since aren't getting the warning beep....I would drive it and just check it from time to time. IF the fluid is old then a full 'flush' with new fluid would be good, but I wouldn't expect it to change the test results much (if any) unless you have air in the system.
My original plan is to change this whole unit when my truck hit 200k, at least in this fall...I hate work in the summer. So if I want to fix this, seems the only way is at least to change the pump motor? And is this 4705060043 the complete unit for replacing the whole thing?

 

flintknapper

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Yes, that is entire unit.

I was able to replace just the pump motor and accumulator for about $800.00


New1.jpg
 
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Yes, that is entire unit.

I was able to replace just the pump motor and accumulator for about $800.00


View attachment 2669319

Ok, after review many of the posts from the forum, I just ordered all the tools for a full flush. Based on the research, I think we basically need two main processes for the full flush, the first is some regular flush, the second is abs flush with Techstream. And I assuming that if I replace the whole assembly then after the replacement I have to do this again. Please let me know if my understanding right? Thank you, sir!
 

flintknapper

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Ok, after review many of the posts from the forum, I just ordered all the tools for a full flush. Based on the research, I think we basically need two main processes for the full flush, the first is some regular flush, the second is abs flush with Techstream. And I assuming that if I replace the whole assembly then after the replacement I have to do this again. Please let me know if my understanding right? Thank you, sir!

Correct. Flushing the system or a new installation are both basically 'bleeding' the system.

So to insure there is no air trapped in the ABS system, it must be activated a few times while there is pressure on the system to carry out any air bubbles in the fluid.
 
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Just finished. brake feel is impoved, and the pump seems quieter and doesnt kick on as often.

for some reason my master part was red? Looks the same otherwise

08C94762-5E9A-4E39-B3B6-D26A1C4349FE.jpeg
 
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