Brakes: Pedal goes to the floor. Causes?

[ddub]

55 Speedster, power brakes of course. Last year we flushed the brakes, filled with DOT 3, properly bled, worked great. Got it out this year and no pedal. Can get pedal by pumping the brakes. Looked in the cylinder and it looked a little low, did not fill. Went out the next day to fill but now looked full. Still the same response, no pedal but could be pumped up. In reading on the net, the best idea I could come up with is replace the master cylinder. What do those of you in the know say?

[StudeRich]

The signs of an internally "Bi-passing" Master Cylinder.

I hope we are not having the "Chinese" Rubber Syndrome issue on those as well as the previously reported Wheel Cylinder Cups and Boots. It's not enough that we have the "Chinese Flu".

[doofus]

Sounding more like you have some air trapped in the system. M/C level changing like you describe would indicate this. a good 2 person bleeding session might help a bunch. dont be frugal, let out lots of fluid and have an experienced helper on the pedal feeling for a change in pedal feel. Luck Doofus

[Jeffry Cassel]

These things with the mc under the floor can be a real bugger to bleed. Espescially when they have a pb booster. Bleed the booster first, then go to the right rear, the left rear the right front and lastly the left front. The ideal would be to have a helper and a vacuum bleeder. Most of us don't have a vac. bleeder and my helper got married and moved to Oregon to play dodge the rioters. I have an old heavy bottle. I crack the bleeder, put a length of hose over it and submerge the other end in the bottle. I've gone thru 2 qts of brake fluid before getting a semblance of pedal. I got hold of a master cylinder that did not have a check valve in it. Check that out. The mc could be bad . We are not living in the age of excellent replacement parts. Doofus is right- just keep at it--we did not get into Studebakers 'cause they're easy---we just need more frustration in our lives.

[E. Davis]

I made a "power" bleeder out of an old weed sprayer. It was the only way I could get a complete bleed especially since I wore out my wife's leg and she refused to help me again. You tube has a good instructional video on how to make the bleeder. It is easy and really works well. Matter of fact I have it loaned out right now.

[Brianbo]

An old muffler and brake guy gave some solid gold info in my youth. I had replaced a brake hose on an old car and he casually said that I will need to replace the master cylinder within the month. He said that pedal bleeding the brakes drags the piston and seals thru areas of the bore that have not been used in years. The walls of that part of the bore are rough, rusty and will destroy the seals. A new master cylinder is cheap insurance.
Brian