no rear brakes....but calipers are geting fluid...

[down4thakrown]

i got rear disc brakes on my 1 ton 81 k5 and i had a rear leaking brake hose...so i fixed it and went to bleed brakes and noticed that the fluid just flowed out of bleeder did not spray out...and then noticed the new caliper i put on with the line did not clamp the rotor...and the pedel wouldnt move once the bleeder was opened...so i put a new master cylinder on it from a 77k10 that i had under warranty the new caliper closed but still no rear brakes.even jacked up both tires off ground and put in gear and tires wont even slow down when brake is on....front brakes work great...power brake booster is working properly and goes to floor with master cylinder offf...but not with it on...could it be paportioning valve?

 

[76zimmer]

how is your flex hose from frame to axle....sometimes those will swell shut.

 

[down4thakrown]

its a steel braided pro comp hose..are those known for swelling shut.. i guess i should look for a bent metal line maybe?

 

[4xcrazy]

crack the line loose at the t-junction on the rear diff and pump the brakes, i had something cause a rear brake issue with me once while out wheeling, i thought for sure it was a dead master cylinder, went through the headache of replacing that, only to find out it wasn't the problem.

not sure exactly what it was, but something in the system found it's way to that junction, and clogged the line feeding the rears. had fluid coming out, but like you mention, not enough to actually give enough pressure to activate the calipers.

 

[down4thakrown]

crack the line loose at the t-junction on the rear diff and pump the brakes, i had something cause a rear brake issue with me once while out wheeling, i thought for sure it was a dead master cylinder, went through the headache of replacing that, only to find out it wasn't the problem.

not sure exactly what it was, but something in the system found it's way to that junction, and clogged the line feeding the rears. had fluid coming out, but like you mention, not enough to actually give enough pressure to activate the calipers.

well.......cracked the line at the t junction..still no pressure...then cracked the line at were hard line meets the steel braided line...still no pressure...cracked the juntion between the 2 hard lines half way down the chassis...still no pressure.....just drippin...then tried loosing hard line aat porportioning valve and it ended up breaking...didnt realize i was twisting the metal line....but got it off even the big fitting and took the spring out with the valve looking piece and still no pressure... i then loosend the line at the master cylinder and it squirts to the fender......im thinkin ethier line to the portioning valve or portioning valve it self....but now i gota fix the hard line goin half way down the chassis......

 

[4xcrazy]

well, you're doing exactly what i did, go from the wheels forward cracking open lines and testing till the pressure is a present and correct.

I just happened to not have to go that far

 

[down4thakrown]

yep....after seeing how much a new proportioning valve is ...i think im goin to pull a used one...

 

[rufusbooth]

Disk/Disk proportioning valve to match your rear disk conversion. $59

http://www.speedwaymotors.com/Disc-Disc-GM-Proportioning-Valve,13539.html

not sure if that is cheaper than what you found but it should work for you.

Cheers,

Rufus

 

[howdiy]

Someone once told me there is a safety valve or something that goes on when your rear brakes are leaking that limits the pressure.

My rear breaks were doing the same thing but one day they just started working again.

 

[down4thakrown]

Disk/Disk proportioning valve to match your rear disk conversion. $59

http://www.speedwaymotors.com/Disc-Disc-GM-Proportioning-Valve,13539.html

not sure if that is cheaper than what you found but it should work for you.

Cheers,

Rufus

is this a direct bolt in? or would i have to reflare my lines?

Someone once told me there is a safety valve or something that goes on when your rear brakes are leaking that limits the pressure.

My rear breaks were doing the same thing but one day they just started working again.

ya i was told the same after i went and checked every part of the linne and breaking the hard line that goes the portiioning valve and along the frame rail to the rear brakes....im sure thats what it was cuz my truck sat for a few months and had plenty of time for all the rear brake fluid to drain.....but when i broke the rear hard line i took out the big adapter fitting and the valve and spring fell into the dirt/sand.....so i think im just goin to replace the whole thing...can i just reflare the line i broke?

 

[nvrenuf]

Did you bleed the master cylinder by itself?

Imo, it sounds like you still have a lot of air in the system and it needs more bleeding.

 

[rufusbooth]

is this a direct bolt in? or would i have to reflare my lines?

I believe it is a direct bolt in but do confirm by looking at the PDF on the same page. It documents the dimensions and line sizes. Compare you yours and see if it will work. I did compare the dimensions and it will work for a 73 blazer but your mileage may vary.

Cheers,
Rufus

 

[down4thakrown]

Did you bleed the master cylinder by itself?

Imo, it sounds like you still have a lot of air in the system and it needs more bleeding.

i did..then when i bleeded the lines when i would open the line and let the pressure out the brake pedal wouldnt budge at all...then after do it for a while still no results...im thinking im goin to just run a t fitting for the front and a adjustable proportioning valve for rear...

 

[down4thakrown]

just a follow up jus incase anybody was following this thread....well after realizing my lines i reflared wernt even holding fluid and were leaking i think it wasnt holding enough pressure to close the calipers thus why the rear braks wernt workingand after trying and retrying to reflare them so they would hold fluid and pressure, after my fingers were about to split open i gave up and took it to a shop to have them do it....and put in a 1980's corvette proportioning valve in it and they work great..thanx for the advice fellas.

 

[Fordum]

Hey, thanks for posting the followup. That is the only way we can learn. Folks here are pretty good about it, but sometimes a thread will run along for a while, and then we never know what the ultimate result was.

Glad you got it fixed.

J.