Replacing hydraulic brake booster motor, '03 4runner

[SF03runner]

Hello all,

The electric pressure boosting motor that sits under the master cylinder is dying. It wasn't building pressure nor activating and I had an alarm going with a stiff pedal and nearly no brakes. I got it to come back to life by hitting the side of the housing to unstick it and get pressure back, and the fluid is normal, so I'm nearly 100% certain I've found the problem.

Anyway, I'm not in a position to yank the entire assembly out, so I'm going to remove just the motor and leave the pump/accumulator and everything else alone.

Question 1) has anyone successfully yanked the motor while leaving everything else in place? It's two 5mm Allen bolts, but the back one is hidden with a bunch of hard metal lines in the way. I can feel the bolt with my finger tip and I've read here two people managed to remove it with various u joint socket adapters. I ordered various extensions that arrive today but any guidance would be useful!

Question 2) if I manage to swap out just the electric motor but nothing else, should I still need to bleed anything? I'm hoping it's not necessary since I'm not disconnecting anything with fluid nor the accumulator.

Thanks for any advice you can give me!

 

[AuSeeker]

Hello all,

The electric pressure boosting motor that sits under the master cylinder is dying. It wasn't building pressure nor activating and I had an alarm going with a stiff pedal and nearly no brakes. I got it to come back to life by hitting the side of the housing to unstick it and get pressure back, and the fluid is normal, so I'm nearly 100% certain I've found the problem.

Anyway, I'm not in a position to yank the entire assembly out, so I'm going to remove just the motor and leave the pump/accumulator and everything else alone.

Question 1) has anyone successfully yanked the motor while leaving everything else in place? It's two 5mm Allen bolts, but the back one is hidden with a bunch of hard metal lines in the way. I can feel the bolt with my finger tip and I've read here two people managed to remove it with various u joint socket adapters. I ordered various extensions that arrive today but any guidance would be useful!

Question 2) if I manage to swap out just the electric motor but nothing else, should I still need to bleed anything? I'm hoping it's not necessary since I'm not disconnecting anything with fluid nor the accumulator.

Thanks for any advice you can give me!

Good luck doing it without pulling the entire assembly, I have replaced my entire assembly with a new one, it wasn't all that bad doing it but I have all the tools and the experience of 55+ years of doing my own work, I replaced it with a new OEM assembly and only had to bleed the master cylinder.

I guess it's possible to swap the motor in place but I haven't looked at it with that in mind, you shouldn't have any need to bled anything if you can get it swapped without removing any fluid lines.

 

[SF03runner]

Good luck doing it without pulling the entire assembly, I have replaced my entire assembly with a new one, it wasn't all that bad doing it but I have all the tools and the experience of 55+ years of doing my own work, I replaced it with a new OEM assembly and only had to bleed the master cylinder.

I guess it's possible to swap the motor in place but I haven't looked at it with that in mind, you shouldn't have any need to bled anything if you can get it swapped without removing any fluid lines.

Ok thanks for the advice. I agree it seems semi impossible but I found two old posts here where people supposedly were able to remove the motor with a series of extensions and u-joint adapters. I've already loosened the front bolt, so if I can get the back one out, it's a matter of having clearance to yank and reinstall the motor housing. If I can't do it, I'll have to tow it to the mechanic since a full removal and brake bleed is too much for a clandestine parking garage repair.

 

[SocalSam]

AU above is right. There is little to no clearance to remove motor and accumulator as a unit. The complete ABS unit has to come out. I've done this job twice and I would say medium difficulty. IMO, the hardest part were the four in cabin nuts and brake pedal cotter pin. Several wobblies and different length extensions are needed. Bleed is relatively straightforward without special tools. Both times I did the job, I replaced the pump and accumulator as a unit from Lexus GS300 donors. Cost: $60 plus my invaluable time, lol. Shade Tree bleed:

https://www.youtube.com/watch?v=JM5A8PnjS7I

 

[SocalSam]

Forgot to add, brake failure with hard pedal is actually good news. That means master cylinder is good and pump and accumulator replacement will work.

 

[SF03runner]

Forgot to add, brake failure with hard pedal is actually good news. That means master cylinder is good and pump and accumulator replacement will work.

Thanks, I figured as much. Yes there's near zero clearance and removing the entire master cylinder is more than I can tackle in my apartment's parking lot, so I bit the bullet and bought a new OEM pump+accumulator for $700 and will have the mechanic install it. It sucks dropping that amount of money on a 22 year old truck, but it is what it is. Appreciate all the info guys!

 

[alia176]

I have a spare pump/reservoir assembly from a junk yard so it was easy to remove the pump motor. The motor is nothing special, and it needed new bearings and brushes then it was good to go. I can't imagine the solenoid valves malfunctioning unless debris was introduced into the ABS system somehow, which would be rare.

Have you tried applying positive and negative power to the motor itself to see what it sounds like? If it sounds like ass, then the bearings might be shot.

My vote is to find a local 4runner enthusiast then using their driveway to do the work, if possible.

I've been looking for the ABS motor pics from when I did this work but only found one pic and I'm hoping it belongs to the ABS motor! I've attached it so that you can read the bearing info.

If you need any pics off of my spare unit, pls let me know.

EDIT: never mind, you plunked down the dough on a new one. Congrats!! Was that an OEM unit for $700?

 

[SF03runner]

EDIT: never mind, you plunked down the dough on a new one. Congrats!! Was that an OEM unit for $700?

The options are basically 250-350 for a rebuilt electrical motor, or the entire brand new OEM assembly for 700 plus shipping from various online dealerships. I figure since I'm paying the mechanic 430 bucks to install it, I might as well pony up the extra cash to get a the entire assembly brand new (electrical motor, PLUS the pump, wiring, and accumulator, part 47070-30060) and get peace of mind for the next 200k miles. A low mileage junkyard master cylinder would be another viable option, or just the motor if you're doing your own labor.

I found some old threads here (search for Hawaiian Hillbilly) where they took apart the motor and compared new vs. worn out with pictures. They even sell rebuild kits for 80 bucks if that's something anyone wants to tackle on their own.