HDBobbers
Junior Member
- Joined
- Jul 13, 2016
- Posts
- 21
- Reaction score
- 6
- Location
- Connecticut
- First Name
- EZ
- Truck Year
- 1987
- Truck Model
- R30
- Engine Size
- 350
I'm having some issues with my brake system and need some outside perspective. This is on a 1987 Chevy R30 dually, disc/drum setup.
Problem is that i don't have any braking power at the rear. I can actuate the wheel cylinder. The cylinder will move, but only slightly.
What i've replaced in the system so far:
Master cylinder (bench bled prior to install)
Proportioning valve
Front lines
Front hoses
Front calipers
Rear lines
Rear T block (load sensing valve removed)
Rear wheel cylinders
Rear brake shoes
Rear drum components
- Popped the pigtail off of the prop valve and inserted stabilizing bolt
- System was pressurized to 10psi stable with a Motive Power Bleeder
- Bleeder barrel was filled and pressurized to 15psi and bled rear left (furthest, line runs on right frame rail), rear right, front right, front left
- Shoe adjusters dialed out for full contact with drum, then backed in slightly
At this point, I put the axle back together and started the vehicle, put it in gear, and let the rear turn (truck is on jack stands). Depressed the brakes and they are soft, though they have always been soft since i bought the truck. The rear continues to turn.
Took the rear apart, started the truck, and pressed the pedal with a long board while watching the rear brake system. I can see the wheel cylinder moving... but only slightly.
I'll mention that if i press the brakes to the floor, i am met with some odd constant jittering and what sounds like power steering screech. Could this be a failed brake booster? Aside from the rear brakes not actuating correctly, the only thing i can think of that would cause some sort of hydraulic screech or throwback on the pedal would be the brake booster, though I have never needed to replace one.
Anyone have some thoughts?
Problem is that i don't have any braking power at the rear. I can actuate the wheel cylinder. The cylinder will move, but only slightly.
What i've replaced in the system so far:
Master cylinder (bench bled prior to install)
Proportioning valve
Front lines
Front hoses
Front calipers
Rear lines
Rear T block (load sensing valve removed)
Rear wheel cylinders
Rear brake shoes
Rear drum components
- Popped the pigtail off of the prop valve and inserted stabilizing bolt
- System was pressurized to 10psi stable with a Motive Power Bleeder
- Bleeder barrel was filled and pressurized to 15psi and bled rear left (furthest, line runs on right frame rail), rear right, front right, front left
- Shoe adjusters dialed out for full contact with drum, then backed in slightly
At this point, I put the axle back together and started the vehicle, put it in gear, and let the rear turn (truck is on jack stands). Depressed the brakes and they are soft, though they have always been soft since i bought the truck. The rear continues to turn.
Took the rear apart, started the truck, and pressed the pedal with a long board while watching the rear brake system. I can see the wheel cylinder moving... but only slightly.
I'll mention that if i press the brakes to the floor, i am met with some odd constant jittering and what sounds like power steering screech. Could this be a failed brake booster? Aside from the rear brakes not actuating correctly, the only thing i can think of that would cause some sort of hydraulic screech or throwback on the pedal would be the brake booster, though I have never needed to replace one.
Anyone have some thoughts?
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