Brakes keep failing

[Doidge1990]

My 1981 Aircooled brakes keep failing. One min i have brakes, the next my foot can be flat to the floor with no brakes. I almost have to pump them back up then they go again. they can be really hard then they go again,The worst bit is its intermittent as they can be fine then for a while. nothing worse than thinking you have brakes and you havent.
Any ideas of things i need to check or change?
Thanks in advance

[jamesc76]

Master cylinder failing would be first thought in my head, and defo needs sorting asap

[nordberg]

Have you checked the fluid level in the reservoir? I know that the brake and clutch use the same res so maybe you would experience issues with both?

[shaky]

Master cylinder failing would be first thought in my head, and defo needs sorting asap

When this happened to me it was the Master cylinder as James has stated. If you are not a competant home mechanic then it is a garage job pronto.

[Ralf85]

I second that- get a garage to check it out and fix it. With an early air-cooled you should have a clutch cable so a lack of fluid would not affect the ability to drive the van.

[Mocki]

master cylinder......

[a1winchester]

Have a look at this.
https://www.youtube.com/watch?v=ZJ3lrcxNnio

[Mr Bean]

This can happen after a considerable time when the initially sharp flexible lip on the piston rubber becomes worn and relaxed preventing the back pressure which assists in sealing the piston rubber against the cylinder wall. As the man says if you snap the pedal down quickly it can seal but push it down slowly the pedal will go to the floor. So yes in my opinion it would almost certainly be the master cylinder failure.
CS