brakes locking up!!! help please!!!

[4.2L_Guy]

ok im pissed... i just paid ford motor company 200 bux to fix my brakes... and they are worse then when it went in the shop!!! everytime i step on the brakes the back brakes lock up... i mean if i step a little to hard they lock up and i can feel the pulse on the peddel... i took it in they said a seal was leaking... so i said just do whatever needs to be done to give me my normal brakes back... and they did... they worked like brand new for about a week then ever since then they have been locking up whenever i come to a stop... they are so touchey... its pretty much either all or nothing. can you tell me what is going on? casue ford motor company cant... and neither can midas... took it to both of them and the brakes worked fine for about a week after they worked on it.... but the gradually got bad. im pissed about the hole deal... can you guys help me out before i donate to ford again.

any replys are greatly appreciated thank you

[mkosu04]

Do you have ABS? You mention a pulse in the pedal which I assume is ABS.

Either way, it sounds to me like your proportioning valve is bad. I believe your truck should have a load-sensing prop valve. This is used to reduce the pressure to the rear brakes. But if you have a heavy load, it allows more pressure to the rear brakes so that you get better braking performance (the heavy load increases the wheel friction so you can apply more stopping force)

If your prop valve has failed and is letting all the pressure go to the rear wheels then you would quickly lock them up. At which point your ABS would step in and that is why you feel the pulse on the pedal.

[4.2L_Guy]

Originally Posted by mkosu04

Do you have ABS? You mention a pulse in the pedal which I assume is ABS.

Either way, it sounds to me like your proportioning valve is bad. I believe your truck should have a load-sensing prop valve. This is used to reduce the pressure to the rear brakes. But if you have a heavy load, it allows more pressure to the rear brakes so that you get better braking performance (the heavy load increases the wheel friction so you can apply more stopping force)

If your prop valve has failed and is letting all the pressure go to the rear wheels then you would quickly lock them up. At which point your ABS would step in and that is why you feel the pulse on the pedal.

yeah i no about the abs and stuff... thank you for the help!!! i needed it... i will take it in soon and tell them... thanks again