brakes.....help!

[junktruck]

I posted back in october about a problem i was having with my brakes, at normal braking pressure the back wheels lock up, i have changed the front calipers because i thought originally it was the front locking up but then i found it was actually the back wheels locking up.I was told there may be air in the lines so i bled the brakes , it didnt help. My question is now, and im assuming it is the brake proportion valve, how can i loosen all those brake lines to the proportion valve without breaking them because i for sure dont have the patience to replace all those lines lol. Any help would be appreciated.

[Captkaos]

Breaking the lines as in when you remove them.  Soak them with penetrating oil and use a line wrench..

[ccz145a]

be sure to use a line wrench, it wraps further around the flats on the fitting.

hard to believe the proportioning valve is the problem, though. nothing in there to wear out. sounds like a broken spring in your rear brakes. just one wheel in the back locking, right.

[DnStClr]

Yeah- assuming you checked the springs on the back brakes, you need two line wrenches- a 3/8" and a 9/16" for the fittings on the proportion valve. Also, check the brake line itself for damage- a rock hitting it could have dented the line.

[autorepr]

Slow down there tiger,,,,     If the back brakes lock when you hit the pedal then the hydraulic part is working. Leave the prop valve alone, it's just a fixed orifice. The only moving parts are for the warning switch. And don't bleed the system if it's got air in it it wouldn't push the shoes out.  It's a problem like the drum is out of round or the surface is rust pitted and "grabby". There may be a broken/ weak spring letting the shoe !@#$ and wedge in place when applied. Are the rear brakes adjusted properly? If there's to much travel they can fly out and lock in place. Is cooked rearend grease on the linings? It can act like glue and grab the drums locking it up. Pull the back wheels and drums off, check it good, have someone turn the drums on a lathe. (only take off the smallest amount) Doing so will head off a lot of work for you.