Hello all. I have just replaced the brake master cylinder and wheel cylinders on a 66 beetle and bled the brakes. The pedal is firm to start with and everything is ok. I walk away and come back later and the pedal goes to the floor. If i pump the pedal it gets firm again. Bled the brake system several times and still the same thing happens. What am i doing wrong. any help and advice would be greatly appreciated

is it a twin master cylinder or a single did u change the 4 flexible hoses these could be blocked

you still have air in the system

Yes it is a single master cylinder and i have replaced the flexible hoses on all 4 sides.

Try adjusting the shoes again.

yep adjust the brake shoes

make sure you start bleeding on the rear passenger side first then go to the drivers side rear then front passenger side and finally front drivers side