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Discussion Starter · #1 ·
1986 Chevy K10. Did some work on rear brakes, had to bleed them, let master cylinder go empty. Bled everything but I can't seem to get them to work correctly.

It has
-76 Eldorado calipers at rear
-Stock disc/drum MC
-Wilwood proportioning valve
-Stock combination valve with internals removed, other than the pressure switch/valve which is still there.

All mods above done years ago, at this time I was just adjusting the parking brake and needed to bleed that caliper.
Got carried away and let the rear reservoir go empty. I've tried pretty much everything at this point, just now I:
-Bled master cylinder by disconnecting brake lines and running a short, clear, hose to the reservoirs -> slow pedal pushes until no air is visible.
-Connect brake lines, have a helper push and hold pedal while I loosen and tighten lines at MC. About 5 times both front and rear lines.
-Bled all calipers with a vacuum bleeder, starting from rear right and ending front left.
-After test braking, I also removed rear calipers and bled them with nipples pointing straight up - made no difference (when Installed they point about 2'o clock. I can't remember if I had to remove them for bleeding when I installed them).

The pedal still goes about half way in softly.
When slamming the brakes on loose gravel, there is no lockup of rear brakes. Turning proportioning valve all the way in or out makes no difference.
When jacking up the rear end, 1st gear and giving some gas, the brakes do stall the engine quite well. So I'm really out of any ideas what could the issue be?


3116392
3116393

 

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If you can pump your pedal and it gets higher, then there is air,
If it doesn’t get higher, then it’s just a spongy pedal since you have discs in the rear.
When I bleed brakes I attach a 2-3’ section of clear tubing from the bleeder and tape(or) magnet the line up above the brakes an just open the bleeder and pump the pedal, the fluid and air comes out, the air keeps going up and the fluid gets sucked back in. Do it until no more air bubbles come out then tighten the bleeders and move on.
If you still have issues after that look for a leak in your lines somewhere.


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Discussion Starter · #3 ·
If you can pump your pedal and it gets higher, then there is air,
If it doesn’t get higher, then it’s just a spongy pedal since you have discs in the rear.
When I bleed brakes I attach a 2-3’ section of clear tubing from the bleeder and tape(or) magnet the line up above the brakes an just open the bleeder and pump the pedal, the fluid and air comes out, the air keeps going up and the fluid gets sucked back in. Do it until no more air bubbles come out then tighten the bleeders and move on.
If you still have issues after that look for a leak in your lines somewhere.
Pedal does not get higher with pumping. I took it for a road test after it sat for few days and either time did something, or I was just imagining and overthinking the situation. I think it is working now as it was working before I did anything, there is just that much travel before the brakes start grabbing.

Altought I still think my rear brakes are not working as they should, I have my proportioning valve set to max and it is not braking much at the rear. Front brake piston size is 74mm, and rear is 63mm, both receiving equal pressure I would think the rear brakes should lock up pretty easily.
 
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