87GTAj

iTrader: (4)

I finally got around to installing the new brakes I had purchased for my car and after installing everything, the fronts work great but I don't appear to be getting any movement out of the rears. Here is what I installed:


Front: LS1 calipers (brand new calipers)
Rear: PBR calipers (brand new calipers)
Russel SS lines at each corner
LS1 Master cylinder (was on with the old brakes) [new when installed]
Adjustable prop valve for rear line; plumbed straight from MC to front lines
New hard line to rear axle (was on with the old brakes)


(only stock components are the booster and the hard lines from the master cylinder to the front flex lines)


I had removed all of the components, so I first bench bled the master cylinder, reinstalled, and then bled all of the brakes with a Motive power bleeder in the proper sequence (Pass R, Driver R, Pass F, Driver F). The front brakes hold really well, but the rears don't appear to move at all when the brakes are applied.


I bled until fresh fluid came out at each wheel with no air visible, and I'm confident that fluid can get to the rear brakes. If I attempt to pull the e-brake lever at each rear wheel, they engage and hold the rotor with very minimal force. This makes me think that the pistons are free to move and not frozen. Also, I can't detect any leaks in the system.


I am looking for ideas, because I have sent about 3 bottles of fluid through the system and still have this problem. I am not against re-bench bleeding the master cylinder, but I was wondering if I have overlooked something else that would not require me to perform the bench bleed again.


Any help is appreciated.


Thanks,

Dom.M

Did you replace the flex hoses at the rear? If not these tend to collapse internally with age. They will allow fluid out but not enough for brakes to function properly.

dbrochard

iTrader: (3)

Check to make sure you didn't accidently swap the left and right rear calipers, brake bleeder bolt should be pointed up. I did this by accident and the back brakes had very little power. Fixed this issue, and the car stops quicker than my dads new mustang.

87GTAj

iTrader: (4)

Yes - I did replace the rear flex lines with stainless steel lines.

87GTAj

iTrader: (4)

I will double check this, but I believe both are on the correct side - the bleeders aren't pointed up necessarily, but they are on the high side of the caliper, facing inward if that's what you mean.

87GTAj

iTrader: (4)

Yep - e-brake cables mount at the bottom of each caliper and bleeders are toward the top.

87GTAj

iTrader: (4)

Anybody have any suggestions for what else to check that I haven't already? Worst case scenario, I can shut off pressure to the rears and take it to a shop using only the front brakes, but I'd prefer to fix it myself if I can.

QwkTrip

iTrader: (22)

The brake bleeding process has proved you are moving fluid to the rear brakes. Probably a lack of rear line pressure. What prop valve are you using?

I have C6 front brakes with LT1 style PBR rear brakes, and the rear brakes were pathetic with a SSBC prop valve. Switched to a Wilwood prop valve and the rear brakes perform now. Completely changed the dynamics how the car feels when braking!

The Wilwood unit is adjustable all the way up to 100% (no pressure reduction) and I had to crank it down near to 100% to make the rear brakes perform. When the rear brakes are doing their job, then the brake pedal also tightens up and feels a lot better. The Wilwood valve fixed every problem I was having with my brakes.

QwkTrip

iTrader: (22)

Here are the part numbers I used,

https://www.thirdgen.org/forums/ltx-...ml#post6083021

87GTAj

iTrader: (4)

I have what appears to be an SSBC knock off (no branding on it, but looks like a spitting image of the SSBC). I have tried running the rears at different settings ranging from min, to max, to something in the middle and never seem to get any change in the bite of the calipers (no bite to speak of, actually). I am definitely willing to give a new prop valve a shot if that may be the culprit.

QwkTrip

iTrader: (22)

Yes, I had the same experience. Never felt any difference moving the SSBC from lock to lock.