Almost certainly has the crappy 254mm (10") leading-trailing shoe rear drums.
Master cylinder had a leak so I replaced that and the booster. Was unable to bleed the rear brakes at that point so I took it into the shop and after working on it and re-bench bleeding and flushing the ABS they couldn’t figure out how to get rid of the spongy brake.
I hope the shop didn't charge you, since they couldn't figure out a way to fix this.
Rear brakes wont bleed but the front will. Could it be the hoses? No fluid comes out when you turn the bleeder screws for the rear brakes, only the passenger side gives a little fluid.
Could it be the hoses swelling up?
Which is it--"NO" fluid comes out of the rear brakes, or "a little fluid" comes out of the passenger side rear?
First Guess based on incomplete information: COULD be ABS, COULD be crushed brake tubing, COULD be a plugged rear brake hose. But my money is on air trapped in the master cylinder secondary piston area, which could give both a soft pedal, and little or no fluid to the rear brakes. The other potential problems would tend to give a high, hard pedal rather than a low, squishy pedal.
Properly bench-bleeding a master cylinder takes more effort and time than most folks realize.
Make REALLY sure the rear brakes are properly adjusted, and that the
park brake works and is used frequently.
To center the valve, remove the switch and use a pick or small screw driver to move the spool such that the groove is centered in the switch opening, reinstall the switch.
I have never had the safety switch trip on my GMT400s. Maybe they're different from all the other GM vehicles I've worked on.
MOST GM safety switches are self-centering. I've never had to manually center a GM safety switch.
I have had to manually center two Ford safety switches, though.
