Ok this is my last attempt to figure this out before I give up.

Here is the things I have done:

1. Earls Stainless Steel Lines
2. Fine Lines Stainless Hard lines
3. PBR rebuild install on the calipers
4. New GM 92 Z28 4 Wheel Disc Prop Valve
5. Power bled the system with a Motive Pressure Bleeder
6. All new synthetic fluid
7. New GM Banjo bolts


Brakes still do not stop the wheels from spinning at idle up on jackstands.

All thats really left I presume is so replace the calipers with complete new ones, master cylinder, or power booster.

My front brakes work fine. Fluid runs fine out the bleeder screws.

Any ideas? I am about to push the car off a cliff.

 

Sorry to hear of your on-going difficulties--gotta be frustrating. Did you ever experiement with "free travel"?

JamesC

 

I thought the free travel was only for the ebrake?

 

Could it be that if you adjust the free travel so that the e-brake functions as designed, the brakes themselves will work properly as well? Free travel, as I understand it, is pretty much a pad adjustment. At this point, you have little to lose with a bit of experimentation.

JamesC

 

True one of the hex set screws happens to be stuck tho so gonna have to play with that... worst case I will drill it out , tap, and put another one in. I will post as to what happens.

 

Yep, try the fine adjustment like James mentioned. They rarely need to be adjusted this way but it can happen.

Ed

 

I practicaly mashed the pads into the rotors and no go.

So new calipers, master cylinder, booster, or take it somewhere and get raped?

 

pull off the caliper and but leave it connected. put a block of wood in the caliper, leave enough space fo rthe piston/pads to move, but large enough so the pisont doesn't come out. messy)

Push on the brake pedal and see if it moves. If it doesn't then it is forzeon or no fluid pressure is getting to the caliper. With a helper have someone press on the brake pedal (like manual bleeding brakes) and crack open each brake line fitting going to the rear. Start at the mastrr cylinder and work your way back. I think you will find that ther is fluid going to the prop valve but not out of it.

Then.................

It could be the prop valve too. I have seen the prop/sfety valve on GMs remained shut and only lets fluid go to front. You will need to bleed the fronts to release pressure on the prop/safety valve. Then bleed front to rear, alternating back and forth until the valve is centered. Then bleed like normal. It took me a while the first time it happened to me.

It prevents the fluid from running all out if a line fails.

 

Only problem is the prop valve is brand new....and the stock one did the same thing. So I presume all thats left to replace is calipers, mastercylinder, and booster.

So I started with the calipers since the free travel screw was frozen in place.

I will have them monday I will post what happens.

 

To clarify, they are designed to that! It is not a failure of the prop valve, your was probalby OK. condition.
Try bleeding front to rear until you balance it out.

good luck.
Steve

 

just getting in on this cause I'm planning on doing something similar very soon.

 

try bleeding till all you get is new fluid out of them
i had the same problem until i bleed them now i just have a mushy pedel
but i also did a c4 front upgrade

my rear calipers make a creaking noise when when i push the pedal down but i got them used but i figured id use them till they freeze up but for now they work

also the stock master cylinder and the rest of the brake system wasnt designed to work with synthetic fluid so that could be the problem right there
use the ford dot 3 stuff it supposed to be better then normal dot 3

 

I appretaite all the response. I am picking up the brand new calipers today.

I will throw them on. I have a motive power bleeder Ill throw that on and bleed the brakes till the front ones comes clean too.

Wish me luck.

 

I do. If I'd experienced all the difficulties you have, I might've pushed my IROC over a cliff!

JamesC

 

go get new calipers my experience with these if they are frozen they need to be replaced i once went thru the headache the your going thru i left it gravity bleed one time for 2 days and it still did it thats why this time when it goes back together itll have 4th gen stuff on it

 

The odds that two rear calipers failed at the same time are remote.
Sounds like a pressure problem. Fronts work fine? Must have a good Master Cylinder unless this system uses separate pressure feeds off the Master Cylinder the problem is in the Proportion valve. New or not.

Reading up is necessary to find out the proper way to center this system.
My son's 97 LT1 Automatic has the same issue just discovered. I will look into answers. I suspect a very detailed bleeding recomendation will re center the proportioning valve. GM must have instructions available.

 

I just wanted to post in here saying I finaly got them working. I replaced the master cylinder with a LS1 master and bled the brakes the old fashioned way with a second person.

Also got the new 1LE aluminum calipers on the back thanks to Ed.

 

glad you got this fixed... here's a link to mine if you feel like reading:

https://www.thirdgen.org/forums/brak...ults-prop.html

I don't suggest this method, but it worked for me. There's a couple of other good ideas as well, including switching to the LS1 master as you did.