87 ta 4 wheel discs problems

[hoosiergta]

Cannot get enough pressure on my rear disks.I can stick a srew-driver thru the lug bolts and turn the rotor while someone is standing on the brakes.I've replaced everything but the vaccum booster.(all calipers ,hoses ,lines,proportioning valve, mastercylinder).Has pbr calipers (non 1LE ) I've also bled them countlss times. Right rear to left rear to right front toleft front.
I just don't get it,I converted my sons 92 RS camaro to this same set up and it works fine. Thanks in advance.

[Skip Fix]

If you have the ratchet E brake calipers(I think used until 89) often the ratchet freezes and to piston is too far out. Sometimes you can break it free. Do you use the E brake regularly? You need ot to keep the ratchet working. Might need some new rear calipers.

[6'9"Witha69]

If you have the ratchet E brake calipers(I think used until 89) often the ratchet freezes and to piston is too far out. Sometimes you can break it free. Do you use the E brake regularly? You need ot to keep the ratchet working. Might need some new rear calipers.I've seen this happen many times with junkyard swaps into 2nd gens!

[megaladon6]

is there a metering valve in there?

[hoosiergta]

I never use the E brake, so I'll check that, but I even had this problem after I put new ones on the back...
thank you skip fix.

This is a factory disc brake car, I just wish it worked it worked as good as my son's junkyard swap- thanks 6'9" with a '69

By metering valve, I'm assuming you're talking about the factory proportioning/combination valve. thanks megaladon6

keep the ideas coming. haha

[Skip Fix]

Depending on the prop valve sometimes you have to hold down a pin to get it to bleed if the pressure swirth was activated from low pressure.

There generally are some specific instructions how to adjust the new rear caliper ratchet on installation to get the piston /pads closer to the rotor, so soemthing else that even a new caliper might not cure.

[hoosiergta]

Skip fix- I think that's what the problem is, because no matter how much I bleed the brakes I still have the low pressure light.
I have the GM factory manual so I'll read that part tonite.
Its raining here,and my beater van is in the garage..so I'll work on that another day. thanks again!

[DeltaT]

Worth checking the proportioning valve numbers - they can be very different between years and MC diameters, power vs. manual brakes. They all can look the same, too.

I had the original Malibu prop. valve (for disc/drum combo) on the car with big discs front and rear 12" discs, and I couldn't get the rears to lock up, even with PB. Now I switch to a manual Master Cylinder and the correct prop. valve and the balance is perfect. Got the right parts from Master Power Brakes after I told them what I wanted.

Jim