BB - it is a constant hissing sound when I hit the brakes.....

BB and KenB....No..I did not bench bleed the MC. To be honest I don't think I ran the MC dry but i suppose it could have been down low enough to introduce some air or bubbles in the lines. I will be sure to bench bleed the new MC when I install on Monday, then bleed all four wheels. BTW, I was only bleeding the front....

As far as the constant hissing sound...now what do I need to replace?

Also, how the MC is connected to the brakes...front ( small ) to front wheels - rear ( large ) to rear wheels, which someone said is WRONG...swap them when I install the new MC?

I could cut a hole in the floor and do a Flinstones stop.......

 

Hissing sound- Is it possible you're hearing it only because you're working so close to the booster? Meaning it's normal.

Or a vacuum leak somewhere. Check plastic elbow and grommet on booster for cracks. If hose is dry and hard, replace it. Check for seal at hose/fitting/manifold. Spray small amount of brake parts cleaner to verify any possible leaks.
Once brakes are back together and operating, if hissing is still present but brakes work fine, it's a normal.
If brake peddle is hard as a rock, non existant, or inconsitant, could well be booster problems.
It's difficult to tell at this point.

When bleeding cylinders- You have/Know where, the proportioning valve is? Gently pull out plunger, it won't travel far, less than 1/4", hold in pulled out (small vise grips) position while bleeding cylinders, remember to release afterward. Be GENTLE, don't bend/break.
Bleed in this order-
Master cylinder - bench bleed first
Wheel cylinders-
Right rear
Left rear
Right front
Left front

When complete, doesn't hurt to go back and recheck bleeding to make sure all air is gone, just be sure it's done in same sequence again.

Never let master cylinder run dry, or you'll have to start all over again.

I believe the large bowl on master cylinder should be for the front brakes, but I'm not positive. Maybe someone else will chime in to verify.

Curious question- You aren't going to try to get brakes functioning with existing MC, you've made decision to wait for replacement?
Just wondering why you're not trying, thought this was time critical.

 

a couple things you have options anymore when it comes to bleeding brakes ther are now speed bleeders available which are a one way chaeck valve in a bleeder screw no more pumping up then bleeding off and repeat, you can also get the suction version of bleeder which is very effective, it sucks fluid through the lines no pumping period. works really nice to flush the lines too.

 

I didn't see where you had the drums turned ? If the drums arn't turned and trued the same size ID, it may pull to one side. If it pulls too the left most of the time there is something wrong with right. Do you have the short shoe up front one each side?? If you are doing the bleeding yourself open bleeder on the right wheel fill master and let it bleed it's self then close do the other side close.. refill master put cover on it, pump pedal 1/2 strokes repeat bleeding all air should be out. Now readjust brakes. New brake lining, shoes take 300-500 miles to seat, where they stop good with less pushing down on the pedal. To adjust backing up the truck dose not need to stop! It only needs to torque the shoes enough to activate the adjuster.. 5-7 MPH in and stump very fast as to many times.. The old rule was tighten til no movement then back off 5. Onething you don't want to over is tighten and have them lock up when your stopped.. My 2 cent OLD Brake man 40+ yrs ago..
orich