2003 v8 brake booster pump diy fix

[dms31986]

Question....can I remove the motor only without messing with the pressure? Or is there a process of removing pressure if any first? I have same symptoms. Also, where did you find replacement parts (brushes) for the motor?

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[AuSeeker]

Very good write-up and I'm glad that everything worked out for you. Seems like the motors end up popping off on these systems more than anything, so for those who aren't feint of heart it's a worthwhile solution.

If you ever find a rebuild kit for these please update the thread with part numbers, I haven't seen anything last I checked; but I'm just one guy. Supposedly some member said he rebuilt these things but he/she never provided any further information, so I suspect they were a "click-bait" spammer.

Thanks Hawiian Hillbilly for this topic, very valuable for those who wish to attempt to repair what is a very expensive part to have to buy!!

I have read several times on the forum where BlackWorkInc has stated that he hasn't been able to find a overhaul kit so I'm also bumping this topic to add that there is indeed a overhaul kit for the actual master cylinder portion of this assembly and I know new OEM motors can be found on eBay for aorund $500+/-, as far as the rest of the componets I haven't found any source for them, but it seems the motor and then the actual master cylinder O rings going bad seem to be the most common failures of this assembly.

Here the part number for the master cylinder overhaul kit...

CYLINDER KIT, BRAKE MASTER, Toyota Part No.: 04493-60350

A link to the kit, you can also find this kit for a few dollars less doing a search, but the average price is very similar on most all sites I've checked.

https://www.toyotapartsdeal.com/oem/toyota~cylinder~kit~brake~master~04493-60350.html

 

[vettestu]

i was able to remove the motor without pulling the entire assembly. both hex head bolts are accessible and by wiggling the pump in its clamp there's enough room to get it out and them remove the leads. UNFORTUNATELY ! the commutator was toast. thanks for this post, saved me from a lost night of sleep.

 

[earthrealm]

Thanks Hawiian Hillbilly for this topic, very valuable for those who wish to attempt to repair what is a very expensive part to have to buy!!

I have read several times on the forum where BlackWorkInc has stated that he hasn't been able to find a overhaul kit so I'm also bumping this topic to add that there is indeed a overhaul kit for the actual master cylinder portion of this assembly and I know new OEM motors can be found on eBay for aorund $500+/-, as far as the rest of the componets I haven't found any source for them, but it seems the motor and then the actual master cylinder O rings going bad seem to be the most common failures of this assembly.

Here the part number for the master cylinder overhaul kit...

CYLINDER KIT, BRAKE MASTER, Toyota Part No.: 04493-60350

A link to the kit, you can also find this kit for a few dollars less doing a search, but the average price is very similar on most all sites I've checked.

04493-60350 - Genuine Toyota CYLINDER KIT, BRAKE MASTER

how easy is it to change this oring ??, you have any tips or instructional video?.
i changed the accumulator on my truck, and issue still remains, so the leak is probablly from somewhere else, the o-ring perhaps???

 

[AuSeeker]

how easy is it to change this oring ??, you have any tips or instructional video?.
i changed the accumulator on my truck, and issue still remains, so the leak is probablly from somewhere else, the o-ring perhaps???

I have never had to do anything to my master cylinder or booster.

Exactly what issue are you having?

That being said when [MENTION=66389]BlackWorksInc[/MENTION] said there was a master cylinder kit I kept looking until I found it to help anyone who needed it.

When you replaced the accumulator did you also replace the old O-ring for a new O-ring for it, if not that could very well be your issue?

The booster system, i.e. the electric motor, accumulator are a different system than the master cylinder, the master cylinder itself works just like any old school master cylinder for the most part, there are several O-rings on the piston, the booster system simply supplies extra braking force just like the old school vacuum boosters did in the older vehicles, it's just works using hydraulics instead of a vacuum.

Maybe [MENTION=66389]BlackWorksInc[/MENTION] could provide some more insight if he see this since he has disassembled one of these before.

 

[earthrealm]

[MENTION=149207]AuSeeker[/MENTION], my issue is this : the system is not holding pressure under sustained braking, especially in stop and go traffic, i believe it has a leak, somewhere, thus the pump cant keep up with re-presurring the system under sustained brake usage, some others said they resolved the problem after changing the accumulator and o-ring, mine wasnt resolved, though it got slightly better.

if i keep my foot on the brake pedal continously for about 5mins, the system will fail..and the alarm will start buzzing, i take off my foot from the brakes and idle for a min or 2, the pump will then repressurize the system, and the buzzing will stop and everything will be ok again.

 

[MY06T4R]

5th Gen Brake Upgrade

I was so glad to see that it was an easy fix gang! Now the wifes 'new to us" 03 T4R V8 will be on the road today after I get the front axles and calipers changed out. Will post pics of that as well. Shes diving to the right when I hit the brakes now so I'm assuming front calipers are frozen or about to be....hate these things on our runners. Ive read a few threads in here about the 5th gen or fj caliper upgrades but was wondering what the part numbers are on those. Especially with the differing rotor diameters on our 4th gens. Someone please inform....mahalos all! HH

I had stuck calipers on my 2006 v8 runner, I ordered power stop s6278 for the front and power stop s2736 for the rear with Wagner pads and OEM toyota rotors for a 2010. I also bought the OEM toyota metal brake lines from the rubber hose to the caliper. And it all fit great no modifications needed. Haven't had any problems. :first:

 

[AuSeeker]

[MENTION=149207]AuSeeker[/MENTION], my issue is this : the system is not holding pressure under sustained braking, especially in stop and go traffic, i believe it has a leak, somewhere, thus the pump cant keep up with re-presurring the system under sustained brake usage, some others said they resolved the problem after changing the accumulator and o-ring, mine wasnt resolved, though it got slightly better.

if i keep my foot on the brake pedal continously for about 5mins, the system will fail..and the alarm will start buzzing, i take off my foot from the brakes and idle for a min or 2, the pump will then repressurize the system, and the buzzing will stop and everything will be ok again.

When you replaced the accumulator and O-ring, did you put any oil/brake fluid/lubricate on the new O-ring?

If not then it's possible the new O-ring got pinched or cut and is not sealing well enough, but since it seems that you're only losing pressure while the pedal is depressed this might not be the issue, do you get the same issue if you just hold the brake pedal down and not pressing it repeatedly?

Other than that I don't know enough of how the booster assists the master cylinder, i.e. you have the electric motor that powers the booster pump that builds up pressure in the accumulator, how that pressure assists your foot pressure in the master cylinder I don't know, it sounds like you have a leak somewhere after the accumulator where it's assisting the master cylinder, I would think there's another O-ring/s or gasket at where the pressure assists the master cylinder when you depress the brake pedal, hopefully [MENTION=66389]BlackWorksInc[/MENTION] will see this and hopefully has some input.

 

[earthrealm]

When you replaced the accumulator and O-ring, did you put any oil/brake fluid/lubricate on the new O-ring?

If not then it's possible the new O-ring got pinched or cut and is not sealing well enough, but since it seems that you're only losing pressure while the pedal is depressed this might not be the issue, do you get the same issue if you just hold the brake pedal down and not pressing it repeatedly?

Other than that I don't know enough of how the booster assists the master cylinder, i.e. you have the electric motor that powers the booster pump that builds up pressure in the accumulator, how that pressure assists your foot pressure in the master cylinder I don't know, it sounds like you have a leak somewhere after the accumulator where it's assisting the master cylinder, I would think there's another O-ring/s or gasket at where the pressure assists the master cylinder when you depress the brake pedal, hopefully [MENTION=66389]BlackWorksInc[/MENTION] will see this and hopefully has some input.

YES i get the same result, if i depress the brake pedal continously in excess of 3minutes, the system would not cope, and the buzzer will come on, with all the lights, if i also engage the brake pedal intermittently, in serious stop and go traffic, same issue.

my theory is that i have a leak somewhere, if it was the accumulator, i believe brake fluid may be seen leaking from the accumulator. so i believe its an internal leak, so am suspecting the o-rings in the assy as highlighted in your earlier post, but i dont know where exactly that assy is located, and i dont have another unit to tinker with

 

[AuSeeker]

YES i get the same result, if i depress the brake pedal continously in excess of 3minutes, the system would not cope, and the buzzer will come on, with all the lights, if i also engage the brake pedal intermittently, in serious stop and go traffic, same issue.

my theory is that i have a leak somewhere, if it was the accumulator, i believe brake fluid may be seen leaking from the accumulator. so i believe its an internal leak, so am suspecting the o-rings in the assy as highlighted in your earlier post, but i dont know where exactly that assy is located, and i dont have another unit to tinker with

First you would need to know how a basic old school master cylinder works more or less, the body of the master cylinder has...a cylinder inside of it, the parts you see in the rebuild kit is the piston and related o-rings, etc. that fit in the cylinder, when you push the brake pedal it pushes the piston and forces the brake fluid through the brake lines and pushes in this case the piston in the calipers or in older vehicles the wheel cylinders which presses the friction pads or shoes again the rotors or drums.

Here's a link to photos of exploded views with a couple of cut away photos of many different master cylinders that will give you more insight of the inner parts of a master cylinder.

master cylinder exploded view - Bing images

Our 4th Gens master cylinders have much the same as what you see in the images, except it has the hydraulic booster assembly and the ABS ECU attached to it as well so therefore looks more complicated, and it is but the basic master cylinder is still hidden within all this complicated device we see when we look at our master cylinder assembly.

Somewhere on this forum there's a PDF file from the Toyota FSM that has the steps to overhaul the master cylinder, I have a link somewhere among my many 100s of links on my computer, I will try and find it tomorrow after work if you don't find it searching the forum.

 

[earthrealm]

Just putting this out there for anyone who has this issue, the thread lists the part to buy on ebay

2008 4runner Master Cylinder piston, I found the part # and fixed it!!!

 

[earthrealm]

Ok first off......THANK YOU TO THIS FORUM! Once again after searching through this forum I found a few threads and subsequent links to help me decide what was my next step in diagnosing my wifes 03 v8 4x4 4runner booster pump failure.

Symptoms: FLAT ASS BRAKE PEDAL! has brakes but very evident the booster was not functioning. I needed to stand on the pedal to get the car stopped. No sound coming from booster pump when ignition is turned on.

While searching for parts I quickly found out how EXPENSIVE this piece was! GEEEEESH! Dealer wants near 3500 bucks for a replacement......you can get used pumps and masters off of ebay from $800-$1500 and up! So needless to say I was not a happy Hawaiian hillbilly! However, I did find some good points in this forum which allowed me to tear down my master assembly and narrow it down to the accumulator and booster pump.

So, I took it all apart and focused on the booster pump itself since the problem was either the booster wasn't getting power or the booster was fried. I first tested the circuit to be sure the pump was getting power. At that point I was fairly certain that the problem was the pump itself. So I separated the pump from the accumulator. Then ripped into the pump itself and found that one of the 2 brushes which transfer power to the pump armature was stuck in the off position. Thankfully this hillbilly also owns r.c. cars and was somewhat familiar with how these things operate. I first removed the stuck brush and filed the rubbish off of the brush that was accumulating over the vehicles 271,000 miles. It was pretty gunky in the motor. Then cleaned out the motor replaced the newly "refurbished" brush and spring....and VIOLA! Tested the pump and I had rotation!

Reinstalled everything in its original places on the master and then mounted everything back into the car....followed the procedures (found in this forum) for bleeding the pump and accumulator (key off depress brake pedal 20-30 times then 10 solid pumps and turn ignition on listen for pump to operate) then continue to bleed each caliper normally. I sincerely hope this post will help someone out there save some hard earned cash!!

Here are some pics that I took throughout the journey. This Hawaiian Hillbilly needs my fireball and dissarono on all repair jobs....WOOOOO! 70% FIREBALL and 30% DISSARONO for those who may want refreshment specifics...aloha, HH

The ebay unit i installed about 5 yrs ago has failed yet again. I isolated the problem to be a bad pump and possibly leaking piston. The pump doesnt come on.
I have removed the pump and confirmed that one of the carbon brushes have worn down, and stopped making contact.

I am unable to remove the motor bearing as circled in the pictures below.
2ndly my motor appears to be slightly different from yours. Could you confirm how you were able to remove and reinstall the pump coil?

 

[AuSeeker]

The ebay unit i installed about 5 yrs ago has failed yet again. I isolated the problem to be a bad pump and possibly leaking piston. The pump doesnt come on.
I have removed the pump and confirmed that one of the carbon brushes have worn down, and stopped making contact.

I am unable to remove the motor bearing as circled in the pictures below.
2ndly my motor appears to be slightly different from yours. Could you confirm how you were able to remove and reinstall the pump coil?

Unfortunately I don't think [MENTION=139329]Hawaiian Hillbilly[/MENTION] will respond, looking at his profile he hasn't been back on the forum since 11-30-2018.

 

[space city]

I used a Dremel tool with a diamond cut off wheel to remove the bearing

 

[earthrealm]

I used a Dremel tool with a diamond cut off wheel to remove the bearing

Ahhha..so you got a new bearing?. What size did u get.
Any special tool to reinstall the new bearing?

 

[space city]

Yeah, I went ahead and replaced both while I was in there. But honestly, they were still in good shape. The only way I could remove the bearings, and the commutator was cutting it.


I ordered from Eurton Electric
ABS Toyo kit


Toyota, Lexus, Mitsubishi ABS Pump Motor Rebuild Kit

 

[Thewookie]

Very nice, thank you for this.

 

[MidWesterner]

shootz, brah!

Ok first off......THANK YOU TO THIS FORUM! Once again after searching through this forum I found a few threads and subsequent links to help me decide what was my next step in diagnosing my wifes 03 v8 4x4 4runner booster pump failure.

Symptoms: FLAT ASS BRAKE PEDAL! has brakes but very evident the booster was not functioning. I needed to stand on the pedal to get the car stopped. No sound coming from booster pump when ignition is turned on.

While searching for parts I quickly found out how EXPENSIVE this piece was! GEEEEESH! Dealer wants near 3500 bucks for a replacement......you can get used pumps and masters off of ebay from $800-$1500 and up! So needless to say I was not a happy Hawaiian hillbilly! However, I did find some good points in this forum which allowed me to tear down my master assembly and narrow it down to the accumulator and booster pump.

So, I took it all apart and focused on the booster pump itself since the problem was either the booster wasn't getting power or the booster was fried. I first tested the circuit to be sure the pump was getting power. At that point I was fairly certain that the problem was the pump itself. So I separated the pump from the accumulator. Then ripped into the pump itself and found that one of the 2 brushes which transfer power to the pump armature was stuck in the off position. Thankfully this hillbilly also owns r.c. cars and was somewhat familiar with how these things operate. I first removed the stuck brush and filed the rubbish off of the brush that was accumulating over the vehicles 271,000 miles. It was pretty gunky in the motor. Then cleaned out the motor replaced the newly "refurbished" brush and spring....and VIOLA! Tested the pump and I had rotation!

Reinstalled everything in its original places on the master and then mounted everything back into the car....followed the procedures (found in this forum) for bleeding the pump and accumulator (key off depress brake pedal 20-30 times then 10 solid pumps and turn ignition on listen for pump to operate) then continue to bleed each caliper normally. I sincerely hope this post will help someone out there save some hard earned cash!!

Here are some pics that I took throughout the journey. This Hawaiian Hillbilly needs my fireball and dissarono on all repair jobs....WOOOOO! 70% FIREBALL and 30% DISSARONO for those who may want refreshment specifics...aloha, HH

Yo, HH...thanks for this post. I was crawling the web tring to figure out how best to go about fixing my 03 4runner (also out here in HI) and decided your method is best for the lowest cost. No need to dump hundreds into this thing if im about ot head to mainland soon. Did you have any leaks showing up from your accumulator? just the burnt motor? Im at 196k and there was a slight leak under my unit (bought this used few months back) and I think that is the cause for the pause...no put intended. Mahalo for the post!

edit...kept reading the rest of the thread...he hasnt been on here since 2018. either way, still good info to have from all of this compilation!