BEFORE YOU READ ANY FURTHER... hint... if you replaced the master cylinder and booster as a unit, did you bench bleed the master cylinder before you installed it ???. if not you need to bleed it as well, if i,m understanding you , you bled all the air out of system , you failed to explain what you mean by (the brakes went out ) , there are many ways a brake system can (go out) i,l need to know what happen, did the peddle get (spongy) and go to the floor when he applied the brakes ??, did it get a (hard peddle) he couldn't push the peddle down , what ??
When I have had trouble bleeding systems...I have over come it by reverse bleeding. You buy a pump on container put it on the last bleed screw and flush the fluid back wards up out the resavor
SOURCE: toyota 4runner brake
Did you replace these all by yourself or have them installed ?
Brake master cylinder has to be bench bled and the entire system has to be bled when installed. Or there will never be any brakes. If this is not the problem I need more information in order to diagnose correctly.
SOURCE: 2002 Toyota Sequoia power brake booster % master cylinder are bad
Mr. Clark:
It would be extraordinary for a technician to recommend a booster and a master cylinder with no previous mention from you of a possible problem in this area. In other words, the technician had no business looking at the m/cyl or the booster, unless you told him that your braking was deficient.
Here is what REALLY happened: Somewhere, I'd bet, your brake light came on, and somebody "topped off" the master cylinder, to shut the light off. Now, please understand that the brake fluid level in the master cylinder reservoir DROPS PROPORTIONALLY to the wear of the brake pads. When the tech replaced the front brake pads, he obviously had to squeeze the caliper pistons into the housings to allow the insertion of the new pads. This action forced the brake fluid from the now-compressed caliper pistons BACK into the master cylinder, and it sprayed out from under the cap, coating the cylinder and the booster. Tell that repair service that you do NOT need a booster and a master cylinder, THEY caused the problem with the fluid being everywhere. I am confident that I just saved you a significent amount of money that you do NOT need to spend. Have a great day.
SOURCE: no brakes after master cyclinder and booster replacment
To bleed the brake system open all the bleeders and let the system gravity bleed for @ 1/2 hour ensuring the master stays full. Then close all bleeders and starting furthest from the master (r/r) have someone pump the brakes 2-3 times,hold the pedal down, then open the bleeder,close the bleeder,and repeat untill there are no air bubbles and the brake fluid is running clear .Repeat for all wheels in this order R/R L/R R/F L/F ensuring master cykinder does not run empty. You cannot pump the pedal with a bleeder open you will be sucking air back into the system. Once you finish all wheels repeat to ensure there is no air remaining in system.
SOURCE: 2000 saab 9-3 brakes are dragging after vehicle warms up
Most likely the free play required between the brake pedal and the debooster you replaced.
If all 4 brakes drag,
it can not be anything else, ensure the brake deboost has clearance, between the master cylinder. not partly acitivated already and pushed the master cylinder in slightly. Always look what you did previously and when the problem occurred. Brake pedal to debooster, or debooster to master cylinder both must have some clearance.
SOURCE: i have an 1993 landcruiser
They have air in the system. Keep bleeding them. the air will come out.
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What exactly is your problem, are you having trouble bleeding the system?
Or can you not find the root cause of the failure?
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