brakes

[84chevyk20]

I replaced the front calipers and pads on my truck (84 chevy) and the rotors are great, but it still doesent stop well, i do know that the rear arnt taking as well as they shoud be but i believe something else is the issue... say im slowing down to pull in a driveway.. by the time i turn in ive had my brake on for a few seconds now and the brake light comes on, it will do it everytime and if i stab the brake pedal real quick is how i get it to turn off. the brake light issue started before the poor stopping issue.. also does it matter on the order i bleed my brakes? i did notice under the truck there is a block with a bunch of lines going in and out of it, can this piece cause issues?

[dalaigh]

If that block is on your front crossmember, it's likely the proportioning valve, it makes it so there is more braking power at the front wheels.
When bleeding the brakes always start with the wheel furthest from the master cyclinder, so passanger rear then drivers rear, then passanger front and finally drivers front.
Sounds like your best bet is to replace the rear brakes and flush the system. Theres no sense thinking something else is wrong, if you know the rears aren't up to snuff. Fix them, and if the problem persist move on the the next likely suspect.
As for the brake light, its probably the switch under the brake, either needs adjusting, or replacing.

[RoTuN]

The proper way to bleed that system is to put a long "C" clamp on the proportioning valve to depress the pin at the rear and then you would bleed in reverse order...starting at the closest to the Master cylinder. This is in the factory service manual. The light coming on tells you there is a problem with the fluid pressure differential that the prop. valve is designed for. You may have an issue with the prop. valve itself since the light was on before replacing the calipers. Most of the time when bleeding from rear to front without depressing the pin on the prop. valve you will not get enough pressure out of the rear wheel cylinders to properly bleed. There are rubber seals/ o-rings inside the prop. valve that have most likely deteriorated causing your problem. They can be found for +/- $65.

[RoTuN]

Be careful taking the lines out of the prop. valve...they are probably rusted in, you don't want to destroy them or you will end up replacing the set that goes down the frame rail. Here's a link to prop. valves...........

http://www.performanceonline.com/GM-PROPORTIONING-and-COMBINATION-VALVES-AC-DELCO-172-1353-and-172-1361-TYPE-CHROMED-19296

I bought mine at InlineTube though.

In the picture you will see a rubber cap on the left end of the valve, under that cap is the pin you need to depress when bleeding.