The_Josh_Bear
Full Access Member
Hey guys I haven't been around in a while, but I have a significant brake problem I need help with.
Original problem: rear tires lock up SUPER easily under braking, seems like fronts aren't doing much.
By super easily I mean in my 25mph neighborhood if I'm not paying REALLY close attention AND braking while in gear one of my rear tires will lock up and just drag.
Important notes:
No leaks at any external part.
Wheel cylinders are not leaking.
New shoes installed recently.
Parking brake works great, shoes are adjusted fine.
RABS valve spring removed years ago and fuse pulled. Worked fine all this time and wasn't changed until troubleshooting the issue.
Calipers and pads are new last year, plenty of meat left on them.
Before testing the brakes all 4 corners were bled plus the RABS in this order: RR, LR, RABS, RF, LF.
Things I've done since original problem:
Since my fronts seem to be barely doing anything, I suspected a bulging hose and replaced them both. No change. (they weren't looking good anyway)
Pulled and cleaned out the RABS valve, hoping it would be the problem.
Now the pedal just sinks to the floor. Bled brakes more and then some more, same problem.
******Why oh why don't the front brakes engage even if the RABS is dumping?????? Aren't the two pistons in the master cylinder separate hydraulic circuits???********
Because I bled the system properly I figured the MS was giving up so:
Last night I changed the master cylinder, brand new unit from NAPA. I bench bled it! I installed it, measuring the pushrod and adjusting. I realized after 14 years that the original was too long but yet I never had brake drag issues...dunno what's up with that. Bled brakes as above.
Current problem:
Pedal falls to the floor with engine on, and not real slowly. Rear brakes engage and lock up but less aggressively than before. It's at least sort of derivable now. Today I'll put together a RABS bybass to remove the valve from the equation. I still can't get over not having front brakes if the rears are all screwed up. That sounds like the worst idea ever.
Edit: could this have anything to do with the proportioning valve for the front brakes on the MC? I re-used it when I swapped the MC's. I don't know how they work or if they can break, what makes them tick, etc. Pretty much nothing online about them.
Thanks guys!
Joshua
Original problem: rear tires lock up SUPER easily under braking, seems like fronts aren't doing much.
By super easily I mean in my 25mph neighborhood if I'm not paying REALLY close attention AND braking while in gear one of my rear tires will lock up and just drag.
Important notes:
No leaks at any external part.
Wheel cylinders are not leaking.
New shoes installed recently.
Parking brake works great, shoes are adjusted fine.
RABS valve spring removed years ago and fuse pulled. Worked fine all this time and wasn't changed until troubleshooting the issue.
Calipers and pads are new last year, plenty of meat left on them.
Before testing the brakes all 4 corners were bled plus the RABS in this order: RR, LR, RABS, RF, LF.
Things I've done since original problem:
Since my fronts seem to be barely doing anything, I suspected a bulging hose and replaced them both. No change. (they weren't looking good anyway)
Pulled and cleaned out the RABS valve, hoping it would be the problem.
Now the pedal just sinks to the floor. Bled brakes more and then some more, same problem.
******Why oh why don't the front brakes engage even if the RABS is dumping?????? Aren't the two pistons in the master cylinder separate hydraulic circuits???********
Because I bled the system properly I figured the MS was giving up so:
Last night I changed the master cylinder, brand new unit from NAPA. I bench bled it! I installed it, measuring the pushrod and adjusting. I realized after 14 years that the original was too long but yet I never had brake drag issues...dunno what's up with that. Bled brakes as above.
Current problem:
Pedal falls to the floor with engine on, and not real slowly. Rear brakes engage and lock up but less aggressively than before. It's at least sort of derivable now. Today I'll put together a RABS bybass to remove the valve from the equation. I still can't get over not having front brakes if the rears are all screwed up. That sounds like the worst idea ever.
Edit: could this have anything to do with the proportioning valve for the front brakes on the MC? I re-used it when I swapped the MC's. I don't know how they work or if they can break, what makes them tick, etc. Pretty much nothing online about them.
Thanks guys!
Joshua
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