Spongy brakes

Hi,
I replaced the front brake pads around 4000 miles ago but the brakes still feel spongy. Is this normal for a 1994 T4 Topaz? Is there a way to improve brake performance?
Thanks

As a generalisation, if the vehicle is anything other than vintage/classic, the brakes should never feel spongy. I've driven T4s and the brakes were firm on the examples I drove. The original brakes should not need improving if they are working to original factory standard (though of course most had no ABS - but that's not a simple retro-fit option).

Typical things that can cause sponginess: partial failure of one of the flexible pipes, where the inner part fails and causes the outer sleeve to "balloon". Partial loss of servo assistance. Seizing of a sliding mechanism on single-piston calipers (resulting in the caliper only actually pushing on one side of the disk). Failure of a slave cylinder seal on systems with rear drums (often takes a while for leaking fluid to appear externally). Slight seal failure on master cylinder. No doubt there are other things that are less likely.

Typically, old fluid should not result in a spongy pedal under normal driving conditions (but may do under repeated very heavy braking).

Thanks Caraman,
I assume the brake fluid was changed when the new pads were installed 2 years and 4000 miles ago - but I can’t be sure. MOT in NI are government run and the brake efficiency at the last test was around 60%.
Thanks Roopert,
To me, the brakes have always been spongy since I bought the van three years ago, so part of my problem is me not knowing what “normal” brakes on a T4 should be like. That’s a very comprehensive list of issues to look at and a good place to start investigating.