squishy brake pedal
 

I have a 98gmc z71 that I swapped a 6 lug 14 bolt 9.5 in to about 4 years ago. every thing was working good until about 6 months a go. the brakes fell squishy so I pump the pedal gets firm but rear brakes lock up. I have changed calipers, wheel cylinders & master cylinder have bled the system with power bleeder so many times only new fluid comes out any more. could my problem be the proportioning valve? I have no abs light on either.

Re: squishy brake pedal
 

Any fluid running down firewall inside/outside?

Re: squishy brake pedal
 

not that I have noticed but I will check. it also has braded stainless flex lines.

Re: squishy brake pedal
 

do you have the rubber line going to the back axle or is that stainless too?

one thing i always do when diagnosing soft pedals is start eliminating front or back brakes to see if that helps. if you have the the factory rubber hose in the back just crimp it with a pair or line crimps, ive used vise grips in the past but dont really recommend it then re-drive the truck with the back brakes disabled.

if your pedal is way at the top then you know the issue is somewhere in your back brakes..... you can crimp off you front brakes but i wouldnt drive it very fast or far. no idea if you can crimp off stainless lines