Why won't my rear brakes bleed on my 92 GMC 2500 ?

Question

I changed the leaky left rear whl. cyl. and installed new rear brake shoes. I filled the master, started the truck and proceeded. I was doing the pump & hold method but could'nt get fluid to come out the left rear bleeder. The brakes are now spongy and seems like the rears are not working. The brakes worked great with the leaky cyl. Maybe I should have just left it leak. What's next and how do I get the light to go out? Dave

Answer 1

Sounds like you have a build-up of sludge or a lot of air in your break lines. Continue doing the pump and hold method until something comes out. If you still get nothing coming out check your brake lines to make sure there are no cracks, holes, kinks or bad connections.

Answer 2

i own a repair shop,and what happens some times to them it the proportioning valve gets thrown off center,and it cuts off all the fluid to the rear brakes and when this happens you get no pressure back there all you may have a a lot of air in the system also,,try opening the bleeder screw up,and let it gravity bleed its self it takes a while for the fluid to start coming out of it,buts does a better job than pumping it out if its an old master cylinder and you try pumping it out it usually will damage the cylinder from over pumping it,you can try gravity bleeding and see if that helps, if not id also check the adjust ment on the back shoes they wont work right if there not adjusted right,good luck with it,i hope this help,s

Answer 3

Introduce the brake fluid from the rear wheel cylinder and pump it into the system... this will purge the air (bubble like to go up and not down) and reset the proportioning valve. A good ol clean oil can full of clean brake fluid and a piece of vacuum hose, crack the bleeder open and pump like hell... good luck

Answer 4

If you have the pick-up in the air, and the stands are not under the axle, the weight-sensing proportioning valve thinks there is no weight in the back of the pick-up, and will limit how much fluid gets to the rear wheels.
Place the vehicle either on the ground or on stands. Locate the valve under the rear of the pick-up, and bleed the valve, then the rear wheels (both).

Good Luck