Deuce brake pedal hard but no brakes

I had a dry master cylinder--i filled it with fluid and bled the system from the power brake booster--the pedal came up but is hard as a rock--only goes down 1/2 inch and then seems to push up against my foot--there is almost no breaking--does anyone have any ideas--thanks george

if the truck sat for a long time with no fluid in the master cylinder it may have rust in it and the plunger is binding because of the rust

That just happened to me(hard peddle and no braking) out of the blue. I swapped out my airpack and it is working fine. Sounds like you need a rebuild.

It did sit for 2 years--i did not see anything leaking anywhere and the leval stayed up in the master--if the boster is bad what are ths signs--thanks

I agree with gimp...replace or rebuild the air pack. You may be able to stop (eventually) but it ain't safe to drive.

Try taking the square plug or the 'j' pipe out of the back of the air pack and firing a few squirts of oil in there, airing up the system and pump the pedal plenty and usually that'll do the trick.

Thanks for the help--I will let you know what happens--

Check the bottom of the master cylinder reservoir for rust/crud in the small bleed hole aft of the larger front hole in the reservoir bottom. You might have to draw out some of the fluid to see the holes well with a flashlight. As you slowly move the pedal, you should see fluid squirt up momentarily from the small hole. If not, clear it with a small diameter wire or drill. The small hole is a bleed hole that allows the fluid to slowly return from the system to the master. When it is plugged, pressure remains in the booster and system, and the pedal hard. We have had two trucks with the problem you describe, tore our hair out until we debugged it.
Regards Marti

Thanks for the info

I used all of your ideas--drained the master cylinder and cleaned out the fluid holes in the bottom of it--put oil in the back of the air pack and bleed all the wheel cylinders--the brakes now work well---thanks to you guys for the good info--George

Gem, just so you know, I did the oil in the back of the airpack thing. It helped for a bit, but the original problem came back. Be carefull for the next few drives. I hope it does not return for you.

Proper air pack oiling is in the PM but the only flaw is that it only oils air pack chamber and the air exit valves but not the in coming air side of the valve.
One of my trucks I have plumed with Synflex line and can remove it from the air pack system on the in coming side. There I add the oil and run it through the whole system. Also on this truck I have installed from Home Depot and small water trap to guard the air pack. I had thought about adding an oiler before the air pack to address what I think is a problem. If you have ever rebuilt and air pack you will see that the air valve system has a lot of corrosion on both sides of the valve system.

James--I could not find the PM on the air pack oiling--What did it say--I never thought about oiling the intake on the air pack--thanks