If that's what they say, then do it. I always follow their instructions. I am thinking if you get too aggressive with pumping it, air can get by the seals inside the master(maybe that's why I have to pump it so much sometimes, I am not going slow enough).

 

Yes, GM was famous for stepped bore and a probably 15 degree up angle to boot.

On the question of the correct adjustment on the front shoes, If the anchors are adjustable (Chrysler's were) then you bring the top out first, then back it off just a bit, bring the bottom out till it drags and back it off, then redo the top. You really need a brake shoe setting gauge to do this, it looks like a drum with most of the disc cut off so you can see and measure. You may have a bad MC, it happens. FWIW, 1999 F550 SD uses a 1 3/8" bore master cylinder, it is not the diameter difference but the AREA difference that gets you.

 

I would also like to know...........is their a bypass valve within the master cylinder in that if spring pressure at the drums were to be excessively high ( unmatched master cylinder to the application ) the fluid would simply be bypassed and just remain within the reservoir.............I have thought this often but I guess it looks like I was incorrect in that there is no such thing.

 

So you would agree at this point that if I plug off master cylinder outlets with the caps and the fluid is just re-circulating back into the reservoirs than the master is no good ? That is what it is doing now.

 

No, but your master cylinder is designed for drum rear, disc front, the only bypass you might get is if you bottom the front piston before the rear one. The later trucks (87 up) use an aluminum master cylinder with a screw in residual check valve for the rear.

 

I know what you mean on this tool, I have made one for my early Dodge.

I do not know if it was necessary or not but I thought at the time that I must find a power brake booster that was compatible with the 1986 F-250 brake/clutch pedal assy I am using in the truck ( originally the brake master/booster in this truck were under the cab ) ( all of that either gone or useless when I got the truck ) so that it all would bolt up nice and neat.

The master cylinder I am now using has a few applications, mostly earlier 70s late 60s fords econoline ect. I needed just a hair ground away from the mounting ears so that it would fit on the brake booster studs.

 

Interesting, so no bypass valve, got it

 

The 87-96/7 boosters bolt to the same mount as the 86 booster, I have a 1990 F-250 booster and 1993 master cylinder on my truck right now.

 

If you know of a larger brake master cylinder that will bolt onto my booster than it would be a big help. I will use the one you may suggest in place of what I have now

 

I would give it one more try on the bench, using their procedure, and pumping it a lot before giving up.

 

I will do this in the A.M then, you are right, I am also curious

 

I'm going to second Franklin (Dave).

 

Removed master cylinder this A.M put it in the vise level, filled it with fluid and started pumping but not pumping until it reached its end of travel.

I went back and re-read the instructions given to me with this master cylinder and they said the same thing as the Cordone web-site, just push it in no more than an inch.

As mentioned this is not what I did the first time around but instead continuously pumped it back and forth from end to end.

After literally 80 some pumps I was able to get the piston to only move maybe 3/8 of an inch or so, I continued pumping a little more trying to get it to move a little less, over 100 and no change so I removed it and put it back on the truck and with the plugs still in it felt the pedal, stiff as a board. No movement detectable or very very slight if anything.

I removed the plugs and hooked my lines back up, my wife was here to help me bleed so I started at the right rear upper wheel cylinder. I never did see any major air come thru, little bit but nothing like I thought I would see but I know the lines were never drained so I continued on and we pumped and pumped.

Still nothing major so we went to the right rear lower wheel cylinder, did less pumping this time but still no major air.

Moved over to the left rear upper and continued no major air bubbles but still some, left lower rear I did see one burst of alot of air bubbles.

Went to the front right upper ( fronts only have the one upper ) and pumped quite a bit of fluid thru and nothing major so did the left front and the same.

Hit the brake pedal, improvement, I was able to push hard enough to get all 4 wheels to lock up but not so tight that I could not with enough force still move them but a definite improvement over yesterday.

So I bled them again in the same order, I went thru a little bit more than a pint of brake fluid all together this A.M. just to give an idea of how much we are pushing thru the system.

After bleeding them again we seem to have lost the pedal, it now goes all the way thru until what I am assuming is where its bottoming out on inside the master.

I cannot say it goes to the floor on this truck because it never will, the pedal assy was not designed for this truck so there is no going to the floor, there is the distance from full release until what I am assuming is the full distance of the piston travel within the master cylinder, that is all.

I put my vice grips back on the rear junction line above the diff and since my wife was here had her step on the brake, now we have pedal that will not move much but still the front brakes are not in any way locked up, they do have a bit more drag but I can still move them relatively easily.

I read on-line that if I pump pedal a bunch of times and take the cover off master cylinder and see fluid just jumping out this indicates air in the lines, this is what happens in my case.

Not sure where else to go or what to try at this point, I have considered just opening up all the lines and seeing if the fluid will gravity bleed but I am not sure this will work on this truck, I may still try it though.

I did read-just the rear brakes just to check where I was at, each drum has two adjusters, one at the top on one side of the drum and the other at the bottom of the other side of drum. I backed in the adjustors until I could not move the drum any longer and then backed them up just a bit so there was quite a bit of drag but still moveable.

There is a possibility that there is fluid leaking out the rear bore of the master, I am just not quite sure. I dry it and pump and I guess I do not see anything but then sometimes I think I do. Where it bolts onto the booster, dripping down possibly.

I have a new master still coming this afternoon. Any suggestions on how excatly I can pinpoint what might be going on would be helpful.

I was told by a big truck expert on this forum years ago that these trucks are a real pain in the butt to bleed, he did not give me a reason just said they are difficult.

 

I have seen a couple of mentions of reverse bleeding on the net but its always showing motorcycles, is this any good for trucks?

 

1930 Dodge, is there any way you can get a pressure bleeder, either rent or borrow? That may be the secret to getting all the air out. You have to keep in mind, the original system on that truck had the master cylinder and booster down low.

One other old trick was to put some sealer on the bleeder screw and attach a hose to it so that it can be placed in a container or clean brake fluid. Work the pedal with that screw open. I'm sure part of the difficulty comes from having 6 wheel cylinders.

You might try, mechanically locking the wheels with the adjusters, then bleed. By doing this you quickly eliminate the travel in the wheel cylinders. You should be able to get a hard pedal with almost no travel this way. If it is still spongy, you have air trapped somewhere. FWIW, early VW beetles were a pain, along with some of the Corvettes where the rear caliper was actually horizontal.