REAR(Drum) brakes won't bleed
 

I recently put FRONT DISC brakes on my son's '63 Stepside.

My first problem was with the proportioning valve. The piston somehow got pushed back, and wouldn't allow fluid to the rear brakes. So, I did some research. I completely reassembled the proportioning valve and have it working properly. I know this because, I can disconnect the line from the valve the leads to the rear brakes and fluid shoots out under great pressure whenever the brakes are pumped. Yes, I have the little tool that goes in place of the sensor that stops the piston from moving while bleeding.


Now, for some reason that I can not understand. The REAR DRUM brakes won't bleed.

When I have my son pump the brakes they build pressure. Then whenever I open either if the REAR brake bleeder valves... NOTHING. He DOESN'T LOOSE ANY PEDAL AT ALL. If I have him pump the brakes NOTHING comes out. No air no fluid... NOTHING. And he still has good pedal.

This makes absolutely no sense to me.

I've traced the lines all the way back, no kinks at all. I took the bleeder valve completely out and inspected it. It's fine.

The rear brakes worked fine BEFORE this conversion.


It's obvious that for whatever reason the FRONT DISC brakes are building up pressure, thus the consistent good pedal.

Any ideas or suggestions? thanks

Re: REAR(Drum) brakes won't bleed
 

had a similar issue with a customers truck, did front brake swap on 66, new booster, prop valve and lines. rears would not bleed at all, no air, fluid, etc.

it appears from the pics that you have new or near new lines on truck, what I did to pin point problem,

1. remove line for rear at prop valve, disconnect hardline to flexhose at differential, blow air thru to check to clogged line.

2, disconnect flexhose, both sides, blow air thru to check for obstructions

3. disconnect hardlines to rear wheel cylinders, blow air to check for obstructions

4. check wheel cylinders for movement

the truck I was working on would up having an obstruction in the flex hose. a piece of machining flash (I presume) from Disc/Drum prop valve got stuck in flex hose to rear.

worth checking out

Re: REAR(Drum) brakes won't bleed
 

yeah, that's the only thing that I can think to try.

Just seems odd since nothing on the rear brake lines were touched, but never the less, it has to be there somewhere.

Re: REAR(Drum) brakes won't bleed
 

*UPDATE*

Okay, I completely took apart and rebuilt the proportioning valve(reset the piston), and installed the bleeder valve tool. I checked the REAR output before connecting the brake lines. It had great pressure and stream with each pump of the brakes. I connected the brake lines and start to bleed the rear brakes... SAME EXACT PROBLEM. No fluid or air through the bleeder, and the brake pedal gets pressure.

So... I take off the REAR LINES at the proportioning valve. I take out both REAR BLEEDERS and blow them out, great air flow. I then reinstall the bleeders and unhook BOTH REAR BRAKE LINES, and blow them out, great air flow.

I test the proportioning valve again before connecting the lines and still have a great stream from the proportioning valve. Connect the lines... and SAME PROBLEM.

I remove the lines, test the proportioning valve AGAIN... This time even with the bleeder tool in place, there was no fluid exiting the rear port. RIGHT BACK TO SQUARE ONE!!!!!! UGHHHH!!!!!

I ordered a new proportioning valve(although the one I'm using now is BRAND NEW),... I'll update here after it arrives and I see if it works.

Re: REAR(Drum) brakes won't bleed
 

Did you drill a new hole for the brake rod? I moved mine down and inch and it did help on bleeding the brakes. I dont think I was getting full stroke. Also on my 66 I had a simular issue and ended up pressure bleeding them. Seemed that the front brakes were pulling up tight before I got enough stroke to get the rears to move much fluid. Fooled with it for hours. Pressure bleeding took 15 minutes and has worked great for the last few years.
Jimmy