When i back down my step driveway i have to push real hard on the break to slow down even a little. my other cars do not do this. when the disco is running for while it does not happen. is this a sign the master cylinder needs to be replaced ?? or a vacum leak
1999 D2 120,000 miles

 

First check for a vacuum leak, then it sounds like is might be the master cylinder.
Back into your driveway next time and see what happens in the morning, does it do the same thing?

 

check your brake booster for leaks. When a master goes, it usually goes to the floor, not a feeling like something is bound up. You could also have some caliper issues.

 

Front calipers are new, how do i check for a vacum leak, i will back in garage and see what happens next morning, thanks for the help.

 

This is normal especially if it is the first few times you try braking , first thing in the morning.
Consider pushing the brake pedal a couple of times prior to moving.
By the way what sort of shape are your pads and rotors in??

 

pads and calipers are only a couple of months old. It did the same thing with the old ones to???