I have a 1960 544 with the single stage master cylinder. The issue I have is the pedal travel goes almost to the floor, the car stops. If you pump the brake pedal about twice the pedal comes way up. If you wait a few minutes it repeats the same cycle,goes to the floor two pumps and it almost at the top. It does this sitting still in the drive way or driving.

I have adjusted the brakes and bled them.

I am about to replace the master cylinder to see if that's the problem.

Any ideas appreciated.

Hawk

Are the shoes properly adjusted? Loose shoes cause this condition.
The remark about the the handbrake is pertinent .
On rear wheel drum/front wheel disc cars with this symptom, if applying the handbrake removes the symptom your rear shoes are slack (basically the HB temporarily adjusted the shoe clearance).
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Patrick, '68 220 , '53 GMC 4104, '97 VW Transporter.

The Master cylinder has a return valve that's made of a disc with a series of holes and matching rubber seal. These get clogged with old rubber hose material. Clean and rebuild the master along with brake fluid. Change fluid every 3 years. Check all the brake lines for wetting or leakage. Make sure brakes are adjusted as you only have so much fluid to push to activate the shoes.

Is the handbrake hooked up and operational? If so, does engaging said handbrake make a difference?

I've unknowingly 'adjusted' my brakes the wrong way, more than a few times...
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-Matt I ♥ my ♂

Check to see if you are losing brake fluid, otherwise you need a brake master cylinder.

When the wheel cylinders leak enough, you will see fluid on the backing plates.
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Eric
Hi Performance Automotive Service (formerly OVO or Old Volvos Only)
Torrance, CA 90502