Been stumped on these brakes for a while. 99 Blazer. The abs was completely removed and replaced with a proportioning valve a few years ago from summit. Did great the last 2 years. Last month had a brake line break on the rear axle. Ended up replacing the 1/4 line going down the frame and the 2 rear lines on the axle. The calipers are all AC Delco remanufactured, maybe a year old. The fronts bleed fine, the rears don't bleed normal. I replaced the proportioning valve with a jegs one since there not that expensive and centered it. I'm getting fluid out of the rear, but still doesn't feel right. No leaks whatsoever. Master cylinder is new as well. Bench bleed correctly. Booster is getting vacuum. Rears are extremely hard to press down. Front bleed normal. Takes more than normal pressure to bleed the rears. I use that tool to center the proportioning valve, probably vacuumed a half gallon through the rear to make sure there was no air. Did the normal 2 person bleed afterwards and the rears are still stiff. Extremely hard to press the pedal when bleeding the rears. Any thoughts?

 

What condition is the rear rubber hose in? Original? Check fluid flow before and after that hose. I had one give me fits over that years ago was dry rotted and swole almost shut

 

There all new. I think I've narrowed it down to the proportioning valve. Think jegs sent me a crap one. It's just not putting out enough when the rear line is unplugged from it. Should of stuck with summit. Master is putting out fine. Spits at the valve no matter how many times I recenter it.