brake hydraulics question

I replaced rear shoes on 77 cj-5 last week, didn't rebuild or replace wheel cylinders. This weekend I replaced front bearings and front disc-pads. I have changed lots of brake pads over the years without problems...but now I have a jeep soooo....Here is what I have:
When I pushed the calipers in with a c-clamp it pushed the fluid into the master cyl. Usually I will take the cap off and it just overflows onto the ground. I didn't take the cap off for whatever reason (too lazy to get up and open the hood). Still it should have lifted the cap off enough and overflowed when I pushed the caliper back on the last one I did. Keep in mind I had fair brakes and a good pedal before I started this.
After I got through I pumped the pedal a couple of times to move the caliper and pads out against the rotor. About the time it should have had a good pedal it suddenly went to the floor and I heard something go "squish" at the left rear. Looked and the wheel cyl on the left rear was leaking.
Ok, bought two new rear wheel cylinders and installed them yesterday, tried to bleed the system with a helper pushing the pedal and never could get any fluid out to the cylinders. I can remove the line at the master cyl and hold the port with my hand and get fluid there under pressure when the pedal is pushed.
Is my master cyl suddenly bad or has something happened to the proportioning valve? I have never had a problem with a proportioning valve and am in uncharted territory there. BTW- all the rubber hoses have recently been replaced so I ruled that out already.
Any ideas would be greatly appreciated, thanks in advance.
Ron

 

According to the manual, the combination valve on a '77 with disk brakes does not contain a proportioning section. There is a metering section and a brake warning light section only. The metering valve holds off the front brakes until the rear shoes are in contact with the drum (I presume this is the same as what is usually called a residual valve). On the combination valve, there is a button that must be held down for bleeding. Jeep shows a special tool, but I'm sure you can rig something. It's a button on the front of thew combination valve.

Owning the proper TSM can be very helpful.

 

Thanks, my manual is 410 miles away for reasons not explainable at this time.....I looked at that valve last night and thought maybe that would be the case but my helper had decided she had had enough jeep fun for the evening. Thanks again.
ron

 

If you still can't get enough pressure after doing what Timgr suggested then I suspect the master cylinder went bad. Pushing the fluid back up into the master cylinder is a VERY bad practice. It pushes all the debris that has collected in the lines and calipers back up into the master cylinder so when you push down on the pedal the debris gets into the seals causing internal leakage.
Seen way too many m/c's go bad because of this. When it's a later model vehicle with ABS it can cause very expensive repairs.

 

I open the bleed screw while pushing on the shoes. then close when the shoe is back.

 

X2 :iagree:

 

quick update

I reinstalled the master cylinder which I had removed and done a little close inspection of....no problem found there as I had installed a test jig we use at work for other hydraulics and both sides seemed to work correctly.
I refilled the MC, bled it on the vehicle, proceeded to bleed the rest of the system in the normal sequence with the help of SWMBO....no problems, bled normally, good pedal and good braking. Who knows? Sometimes you just have to step back and take a breather and then do what has always worked in the past.
Thanks for all the input tho.
Ron