I have a 2003 gx470 and the master I believe is the same. Mine leaks out of the front (see picture) Have you guys seen this failure. The BRAKE light comes on but nothing else and the brakes feel fine as long as I keep it topped off. But when full it squirts out and looses fluid quick. I ordered a rebuild kit just not sure it will work, Thanks https://goo.gl/photos/znqEYNnRP1THdUzV8
Master Cylinder Rebuild - DIY (2 Viewers)
- Thread starter Skidoo
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I doubt a rebuild kit (piston ) will fix that, but stranger things have happened, if it's bypassing somewhere.
I expect there is a seal or oring behind that plate that needs changing. It won't be available from Toyota.
I personally would pop the lock ring for a look, then if a standard type oring, go to a brake shop and try to get one, if they don't have one, go to industrial supply, ensure you get one that is not affected by brake fluid. It may be an odd size.
If you have brake fluid leaking, remember it's corrosive to paint etc.
I expect there is a seal or oring behind that plate that needs changing. It won't be available from Toyota.
I personally would pop the lock ring for a look, then if a standard type oring, go to a brake shop and try to get one, if they don't have one, go to industrial supply, ensure you get one that is not affected by brake fluid. It may be an odd size.
If you have brake fluid leaking, remember it's corrosive to paint etc.
Today I had a total brake failure at 70 MPH on the interstate. My brake & ABS light came on along with the audible alarm however I kept driving for about 2 min while testing the brakes to asses the level of action I needed to take. All the while, not realizing that there could be a complete failure of brake pressure within a couple of minutes. Traffic came to a sudden stop and my pedal went to the floor. Fortunately, I was able to cut across three lanes of traffic and run out on the emergency lane. Needless to say it could have been much worse.
I can tell you that I will now keep ear plugs in the car as I had to choose between listening to the alarm for an hour to keep the AC running or sweating it out in 100 degree heat on the interstate while waiting on the tow truck. Oh yeah...and I will be pulling over immediately if the alarm starts sounding. A braking system that has the potential of complete failure is a major engineering oversight. Toyota did a lot of things right with this vehicle but this was not one of them. I can't believe we have not heard of more failures ending in injury.
I am now faced with a dilemma. The symptoms are a complete loss of brake pressure and a reservoir that is filled to the neck. I have not had an opportunity to perform any diagnostics on the vehicle. However, I was hoping if someone can tell me if this is a candidate for a piston rebuild as mentioned in previous posts.
I plan to pull the unit out and test the motor to see if it spins. If not, and I do have a pump motor failure on my hands, the motor seems to be the same unit on a 4 runner. This means they are readily available on the secondary market at a relatively low cost. Does anyone have any thoughts on replacing the pump motor along with a piston rebuild?
My truck is a 98' with 360,000 on it and it might be time to let her go if my only option is a $2000 part.
I can tell you that I will now keep ear plugs in the car as I had to choose between listening to the alarm for an hour to keep the AC running or sweating it out in 100 degree heat on the interstate while waiting on the tow truck. Oh yeah...and I will be pulling over immediately if the alarm starts sounding. A braking system that has the potential of complete failure is a major engineering oversight. Toyota did a lot of things right with this vehicle but this was not one of them. I can't believe we have not heard of more failures ending in injury.
I am now faced with a dilemma. The symptoms are a complete loss of brake pressure and a reservoir that is filled to the neck. I have not had an opportunity to perform any diagnostics on the vehicle. However, I was hoping if someone can tell me if this is a candidate for a piston rebuild as mentioned in previous posts.
I plan to pull the unit out and test the motor to see if it spins. If not, and I do have a pump motor failure on my hands, the motor seems to be the same unit on a 4 runner. This means they are readily available on the secondary market at a relatively low cost. Does anyone have any thoughts on replacing the pump motor along with a piston rebuild?
My truck is a 98' with 360,000 on it and it might be time to let her go if my only option is a $2000 part.
Dam that is bad news, glad no one was hurt.
I've seen one complete loss of pressure. It was when PO ignored sequel of early warn low pad indicator, ignored metal to metal of pad back eat the rotor, ignored sound of piston being eaten by rotor. Finally rotor ate seal pressure was lost, brakes gone. I bought that for $800 for parts, after shop told PO $4K to fix! Cost me $150 to fix,,,sweet!
I've read about guys on the trail loosing pressure from brake line bursting. E-brake saved there butts!
I can't recall hearing of total loss of pressure without a down stream failure (lose of fluid)
Please come back and report your findings, as there is no way to give opinion without more info.
I've seen one complete loss of pressure. It was when PO ignored sequel of early warn low pad indicator, ignored metal to metal of pad back eat the rotor, ignored sound of piston being eaten by rotor. Finally rotor ate seal pressure was lost, brakes gone. I bought that for $800 for parts, after shop told PO $4K to fix! Cost me $150 to fix,,,sweet!
I've read about guys on the trail loosing pressure from brake line bursting. E-brake saved there butts!
I can't recall hearing of total loss of pressure without a down stream failure (lose of fluid)
Please come back and report your findings, as there is no way to give opinion without more info.
I performed a brief diagnostic this morning which included a visual inspection and a computer scan. No codes were thrown and I couldn't locate any leaks following the brake lines from MC to each caliper. The problem seems to be in the MC unit itself. Whats odd is how full the reservoir is now. I check fluids at every fill up and had just check the brake fluid 24 hrs previously. The level was lust under the full mark. Now the reservoir is almost overflowing. So it seems like a good amount of fluid came from somewhere in the system. The only thing I that could think of that holds that much fluid is the pump.
uHu
Bridgeburner
If you read the handbook, or this forum, you would know that the brake fluid level is to be checked with an empty brake booster accumulator, i.e after pumping the brakes 20-30 times. Then, after turning the ignition on and letting the brake booster pump fill up the accumulator, the level will have gone down from full to about half.
360 k on one booster is not bad. I expect you have a failed booster motor, but you'll have to check it to know for sure.
It does indicate booster empty into reservoir. But still shouldn't he have had some brake at bottom of peddle! Would have taken a lot of foot pressure with booster pump down but you still have brakes right?
Easy test is pump peddle 40 times with key off. Turn on key at which time you should hear booster pump start up and run for 30 to 40 seconds, as it draws fluid from reservoir. Once booster is full it shuts off.
Note: It states right on reservoir "key off pump peddle 40 time".
Two weeks on a MC rebuild (spongy/soft & sticking pedal with double pump symptoms before). Bled the crap out of her twice with one ABS activation. Pedal was definitely consistent but still soft. I adjusted the clevis out (lengthening push rod) approx 1.5 turns and pedal stiffness is improved. BUT today I had to brake quickly twice in succession and noticed a very firm pedal upon second push...anyone have this after a rebuild?
My '99 exhibited the problematic double pump to get proper brake/brake pedal response. And even then overall brake performance & feel were a compromise compared to other vehicles in my stable. That is until I did the MC overhaul and new piston install.
But apart of that work I also installed the Stoptech Big Brake kit complete with their calipers. The results, even years later, are significant to brake pedal travel, feel and brake response. Brake pedal free travel is < 1" and after that its solid without any sponginess. I tend to believe the Toyota calipers are partially responsible for some of the ill performance I experienced prior to the work & install.
But apart of that work I also installed the Stoptech Big Brake kit complete with their calipers. The results, even years later, are significant to brake pedal travel, feel and brake response. Brake pedal free travel is < 1" and after that its solid without any sponginess. I tend to believe the Toyota calipers are partially responsible for some of the ill performance I experienced prior to the work & install.
Booster pump assembly did empty into reservoir. I pulled the assembly and tested the motor. The motor spins after I removed it from the MC. What could be the problem is I have considerable corrosion on the bottom of the ABS control unit terminals to the pump. The corrosion is so bad that I can't make out the terminals or screws that held them in place. I have a feeling that this was the cause of the failure. Before I pulled the MC I tested the voltage on the unit at the motor terminals. I was getting less than one volt. Does anyone know if the terminals can be replaced? I don't think they can be reconditioned in the current state they are in.
I fully disassembled the accumulator pump's motor this evening. I was surprised to find that motor is not a fully sealed unit. As to be expected, the motor had a fair amount of wear, corrosion and carbon buildup. The brushes were pretty much gone and carbon covered the magnets. What was remaining of the brushes were damaged and discolored from corrosion. This would be a pretty easy fix as the collector looks to be in good shape as do the bearings. However, the brushes would be hard to locate due to their size. If someone knew where to locate them, you could rebuild the unit easily. I am picking up a used motor out of a 4Runner tomorrow (much cheaper, about $35-$50 from a salvage yard as apposed to $500). Hopefully, this will fix my braking issues. I always had a good pedal, but I will install a rebuild kit while I have the MC out of the car. One thing to note is that the corrosion issue on the connectors at the bottom of the ABS unit was so bad I had to cut the screws out with a dremel. The good news is there are removable nuts on the underside of the terminals that hold the harness in. So once I cut off the screw heads I was able to tap out the nuts. I cleaned up the terminals and everything looks good. This did cause a fair amount of heat transfer to the ABS unit. I am hoping that the heat didn't do any damage. I opened up the ABS and evertyhing appeared to be ok. The corrosion caused the copper to corrode at the terminals and up the motor's wire harness. I will have to create a new harness to connect the new motor. I hope to provide an update one the unit is back in the car.
- Thread starter
- #154
I have not seen any rebuild kits for the ABS section. Even if there were kits I don't think this is something I would recommend trying. Not clear how you would fully test that it was done correctly, some of the circuits are only used in extreme cases. You could find out in an emergency stop a critical seal was not functioning. Add in VSC and you could just be in a hard turn and find its not working.
I rebuilt my MC and am so pleased to say it's working better than ever thanks for the write up!!
HOWEVER...my original problem of the ABS alarm going off when the outside temps get below 25 degrees and won't turn of until the engine has been warming for about 20 min or more. Anyone else experience this? Possible reason ideas?
HOWEVER...my original problem of the ABS alarm going off when the outside temps get below 25 degrees and won't turn of until the engine has been warming for about 20 min or more. Anyone else experience this? Possible reason ideas?
I had the same issue in addition to ABS pump making squeaking noises when it turned on. On a trip to Sierras, in the winter, one fine morning the dashboard lit up. I drove the car slowly for a few minutes while braking gently every now and then. That made the lights/buzzer go away. Did not have a problem for rest of the trip.
However, when we got back from the trip, one day the buzzer started sounding and wouldn't shut up. So I had the ABS pump motor replaced. That took care of the noise and lights/buzzer.
After that, we went back to Tahoe in the winter and I had no trouble from the ABS system, even when the truck was covered in snow. I thought the whole thing was fixed for good. But then, last winter, day after a heavy storm, the ABS lights came back on. Same routine, started the truck, let it warm and it was back to normal.
Few weeks later, I was getting brake pads replaced and the mechanic said something about a blockage in the rear right brake system that he had to fix. After that, the truck has been out in the rain and lights haven't come back on.
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uHu
Bridgeburner
Sounds like water in the fluid. Might have gotten into the booster/pump. It's difficult to get rid of by doing a normal exchange of brake fluid and bleeding at the wheels.
To change most of the fluid, you need to let all the pressure out of the booster accumulator, change the fluid, and activate the abs. If that doesn't help, you might have to take the booster off to empty the system.
Assuming you have checked the state of the booster motor - as there might be humidity there, combined with worn down brushes and commutator.
I've had some success removing fluid from booster by: Evacuating (empty) the booster pump (key off pump brake pedal 40 times), then sucking fluid out of reservoir, fill res with fresh DOT 3 or 4, charge booster (key on), flush all four and then repeat.
Start by timing how long it takes to charge booster from empty (you will hear pump motor), do again after second flush (bleed). Spec is 30 to 40 seconds for boost to shut-off, start timing as soon as key turn on (don't start) after evacuating booster.
Start by timing how long it takes to charge booster from empty (you will hear pump motor), do again after second flush (bleed). Spec is 30 to 40 seconds for boost to shut-off, start timing as soon as key turn on (don't start) after evacuating booster.
Just replaced my master and booster with a used unit out of a 1998 Lexus GS300. Everything went together pretty smoothly. Only two differences:
-the accumulator is slightly smaller
-the R and L fittings into the master are vertical instead of horizontal with the ground.
-had to swap over the reservoir as the 100 series is almost twice the size of the Lexus unit.
Oh, and it cost a grand total of $50 for the unit! How’s that for savings!!!
-the accumulator is slightly smaller
-the R and L fittings into the master are vertical instead of horizontal with the ground.
-had to swap over the reservoir as the 100 series is almost twice the size of the Lexus unit.
Oh, and it cost a grand total of $50 for the unit! How’s that for savings!!!
Did the ABS unit of the GS look like it would match the 100 series perfectly?
