I lost function of my back breaks help!!!!

[lost0138]

ok so heres the problem.. i blew out a back break line again... the first time it happend i had to change it and when i put it all back togethor i lost function of my back breaks but couldnt figure out why about a week worth of driving and the break light suddenly went off and everything was back to normal... well now the other side blew out and i took it to a buddies shop to have it done real quick we swapped it put sume new things and flushed the whole system ... now i cant use my back breaks i have to push the pedal down to far and with 32 inch tires its gettin really hard to stop in traffic .... as for my abs system it dosent work and has a wire cut on the front left tire .. i cant under stand why the back breaks wont work .. when the car is off they hold pedal pressure fine when i start it it goes to the end where front work only but if hit the pedal fairly quickly i can feel the back kinda work as they go to the bottom again does this have anything to do with the abs not working?

[bvr775]

your abs system may be reading slipage and cutting brake pressor. This should not be the case, but i've seen it before with a faulty abs pump. With the wire cut it may be shorting out.

32s"? do you have a supension lift. If your blowing hose your lines may be to short

you may have a blocked line spliter. Check that littel block thing on top of diff that the main goes into and split off to each brake cylender.

check you wheel cylenders

check your brake boster and master cylender

[lost0138]

it happend before but lasted a week or so then kicked in all the sudden the block line splitter is new new lines i heard there was a recall on fualty brake lines tho .. bleed the system flushed it properly everything works till the car is running then it lets out pressure till im at the end of the pedal where only the front work

[20Xtreme02]

Did you bleed the brakes after installing the new lines? Sounds like there may still be air in the system somewhere.

[Sparky2263]

Your combo is stuck in the hold off position. Here's a picture and description;

http://www.sicgmtrucks.com/forum/attachment.php?attachmentid=1641&stc=1

The combination valve has three sections. Each section serves a different function.


The metering, or hold off, section limits front disc brake pressure, allowing just enough pressure to overcome the rear brake shoe springs. When the inlet pressure is below 200 kPa (30 psi) , there is no restriction. This allows for pressure equalization when the brakes are not applied.
The pressure differential warning switch constantly compares front and rear brake pressures from the master cylinder. The switch activates the BRAKE warning lamp when a malfunction occurs in the front or rear brake system. The switch latches in the warning position after a malfunction occurs. To turn off the lamp, you must repair the malfunction and apply enough pedal pressure in order to develop about 3100 kPa (450 psi) brake line pressure.
The proportioning section limits brake line pressure to the rear brakes after a predetermined rear input brake line pressure is reached. This minimizes rear wheel lockup on vehicles with light rear wheel loads.
The bypass feature on the combination valve ensures full system pressure to the rear brakes when there is a malfunction in the front brake system.

(Courtesy Alldata)

[lost0138]

thanks.. hope this works.. theres no air in the line the system was vacum flushed and bleed at a friends shop ..
when i push the pedal a few times hard enough i can build enough pressure for the light to go off and i hear a pop/click when it happens but only at a stopped position and at higher speeds if i push the pedal down hit the gas the pedal gets extremely hard but no rear pressure.. ima see if i can reset something ... havent had to much time to look at it lately been workin to much but ill give it a try tonight and see if i can get this thing working again thanks for the pic and info

[Sparky2263]

Find a dirt or gravel road and work the abs a couple times (try and lock up the brakes). Sometimes this makes for a major improvement by cycling all the valves and getting rid of trapped air.

Oh yeah, never vacuum bleed abs brakes. The equipment mfg. even states this. I don't use vacuum bleeders because the seals are designed to hold pressure. Meaning the pressure insures seal integrity.
A vacuum bleeder can, and will, introduce air into the hydraulic system.

[lost0138]

o... well im kinda screwed on the abs problem since the light as been on since i bought the truck and when i snapped a upper controlle arm it ripped the front left abs wire ... it fixed it self before but this is longer than last time im not sure wut i can do now the abs have never worked.. i tried on a dirt road to lock em up but for some reason my tires dont give in hehe ...didnt know wasent suppoed to vacum them just seemed alot easier with the air compressor self bleeding thing they had at the shop anyone got any other ideas?..ny other way to trip the abs manualy ... if ipump the brakes enough times and hit em good the final time and hold it i can stop alot better but then it juss lets the pressure all out again and im back to front only...im gettin pretty frustrated im rdy to juss take it out

[Sparky2263]

Just pressure bleed them. One guy does the bleeder, says "down", guy doing the brake pedal pushes down (NO PUMPING!), crack the bleeder open, let it flow a bit out and close it before the pedal bottoms out, holler "up", guy lifts his foot off the brake pedal, repeat.

The lazy mans way (my preference when I have time) is a good old fashioned gravity bleed. Crack one bleeder open at a time, let it flow, keeping the master cyl. full, and repeat for each wheel. Good to follow up with a quick pressure bleed (one or two shots at the bleeder).

[lost0138]

o well.. brakes finally kicked in the other day and juss with my luck truck got stolen friday nite they found it but its busted up windows everything stolen so ima find out if im gettin it back or there gonna give me cash for it .. hopefully they give me the money from my system i had almost2grand in it but i have no receipts so who knows