I have a 94 Ford Van (Full Size) with 4 wheel abs. When I first bought it the brakes were great. Now they feel soft and the abs light is on. The brake light is not. Has anyone seen this type of problem before?

If the van is stopped and I press on the brake pedal, it will slowly move down.

Could it be the Hydraulic control unit? Is this a common failure on Ford's with ABS? Is it hard to replace and bleed?

Thank in advance

Andy