new brake system no pressure to the rear calipers

[Rlamas87]

87 Grand National

I converted the front calipers to 2000 S10 blazer, changed all the brake lines from Inline tube also bought inline tube rear caliper conversion kit https://www.inlinetube.com/products/dbk1012gx

new brake booster, PV4 proportion valve with the bleeder tool (to not allow the shutter valve to close) new master cylinder from O'reilly - I bench bleed before the install.

rear is getting little no pressure. I gravity bleed > I had a friend help pump while I release pressure from the bleeder valve and I'm getting flow with little to no bubble in the clear lines but not enough to move the piston to clamp the rotors..

I'll notice the piston slightly moves when trying to build pressure and when I open the valve it sinks back in..

 

[Rt Jam]

Open the line and see if the master displaces fluid. Open at caliper, flex hose then at proportioning valve.

 

[ELCAM]

When you blead the master cylinder was it level? If you blead it at the angle it is installed in the car it will retain air in the very front of the bore.

 

[Rlamas87]

Open the line and see if the master displaces fluid. Open at caliper, flex hose then at proportioning valve.

when I the bleeder valve all the way it displaces fluid from the MC.. just seems like the MC is to weak to move the fluid, not sure if that can be an issue?

 

[Rlamas87]

When you blead the master cylinder was it level? If you blead it at the angle it is installed in the car it will retain air in the very front of the bore.

I bleed the MC level on a bench vise. no air was in the clear lines before I installed to the brake booster and hard lines..

 

[oldsofb]

Had the same issue with a fresh build (New MC, Lines, Calipers, etc.)

Skip to 40:40 where I talk about the rear lines not flowing fluid on a gravity bleed.

Once I got the flow going it was good from there.

Hutch

 

[-dw-]

rear is getting little no pressure. .

When I swapped my 84 to rear disc i had a time to bleed the rears out. Pedal travel was too short to bleed the rears. I opened the front caliper bleeds and left them open while bleeding the rears. Worked for me. Another thought since Ive seen it before several times is make sure the bleeders are at the highest point on the caliper.

 

[gnvair]

Did you swap out the proportioning valve? If not, it sounds like the valve inside has moved. Under normal conditions it should be centered. If there is a leak it will move and shut off the part that has the leak.
You can check by unscrewing the switch from the top. The valve has a notch in the center. If it's not centered you will have have to manually move it back to center.

 

[Rlamas87]

Did you swap out the proportioning valve? If not, it sounds like the valve inside has moved. Under normal conditions it should be centered. If there is a leak it will move and shut off the part that has the leak.
You can check by unscrewing the switch from the top. The valve has a notch in the center. If it's not centered you will have have to manually move it back to center.

new 4 disc PV with bleeder tool.. I'm getting flow but the pressure doesn't seem strong enough

 

[gnvair]

new 4 disc PV with bleeder tool.. I'm getting flow but the pressure doesn't seem strong enough

Which master cylinder are you using?