Can't get rear brakes to bleed on a 4.3l 1990 chevy scottsdale front fine

If your brake hose collapsed internally that will cause brakes to lock to be sure its the hose and not the calipers open the bleed screw and see if the rotor release. If they stay locked then maybe calipers seized try to pry brake pads apart with caliper mounted and brake bleeder open if they return easy then change your brake hose.

if master replaced sounds like air still in lines rebleed the brake lines start with passenger rear than driver rear -pass front -than driver front last..before bleeding check rear brake shoes are adjusted correctly

1990 Chevy 4.3 l engine runs rough at idle half the time-- sometimes it's OK, other days it's rough and can smell raw gas, as tho it's running rich... any ideas?

normally, the brakes are bled starting from the furthest brake to the closest with respect to the master brake cylinder. the sequence is : right rear, left rear, right front, left front. pump the brakes until pressure is built up. do this rather slowly. while keeping downward pressure on the pedal, open the bleed screw slowly. the pedal will go to the floor. hold the pedal on the floor and tighten the bleed screw. do this until no air is observed. keep the reservoir. repeat with the rest of the brakes following in sequence

http://www.aa1car.com/library/2003/bf90347.htm

right rear 1st, then left rear, then right front then left front, this is the same for any car or truck. Always check the master cyl fluid level after bleeding each brake.

Make sure the master cylinder fluid level is not empty,
Then check that a line going to the rear didn't brake on you,or a wheel cylinder didn't let go inside the drum.

bleed each separately

did you see if they need replaced?
and also the emergancy cable may be froze

do you have a self bleeder kit? first off, you have to bleed the master cyl back into its self and the combination valve before you go to the wheels. when you do that, I think you will find that you have air in the lines. disconnect both brake lines from the master cyl and put the bleeder kit fittings on the master cyl, then put the rubber tubing with the kit on the fittings and submerge it in the brake reservoir. make sure its full. then pump the pedal until you get a hard pedal. if that is the case, reconnect the lines to the master, then have an assistant pump up the brake pedal with the engine off, and bleed the combination valve which should be connected to the master by steel tubing. pump it up, then hold it down, and crack the fittings loose, one at a time until the pedal goes about half way down, but do not release the brake pedal until the line is tight again, otherwise you will **** air in the lines. after you do all that, go to the farthest caliper or wheel cylynder from the master and bleed that with the same technique,and dont release the pedal until you close the bleeder screw. unless you have a major prob, this will work.

Check out this link & read about combination valve & how to center it when bleeding.

http://www.autozone.com/addVehicleId,1321403/initialAction,repairGuide/shopping/repairGuide.htm?pageId=0900c1528007a632