There is only 2 reasons for this:
Bad master cylinder
Leak in system.

Leaks can behard to find.  Use water to flush away brake
fluid that was spilled when bleeding.   Dry and recheck for
leaks.
                                                             Eric

Jere Hawn wrote:

> Hi All,
>
> Can anyone provide some assistance on this brake problem?
>
> My pedal fades very very slowly.  So I change the master cylinder and I've
> bled the system from the furthest brake forward no change.  I spoke with a
> local car mechanic and he said that the cups in the cylinder have reverses
> themselves because I did not bench bleed the new master cylinder.  He
> couldn't explain why there was no change from the original master cylinder.
> I checked for leaks: none.
>
> TIA
>
> Jere
>
> 90 GL
>
> 88 GL