just something to think about on this issue.
look the reservoir over good to rule out leaks from it.
look the hose and clamps over good for issues there.
that leaves the pump itself. of all the Gen 3 "busses" ]96-2000] i have owned over the years, i have never seen leakage from the pulley shaft, even with close to 3k miles. the can to pump seal/o-ring seems to be a pretty reliable item as well. however, i have seen the can itself crack, and believe it or not, rust through.
if that is where it is leaking, knock off the rust and get to bare metal around it. same with a crack. then use quick set JB Weld. that will buy you time until you pass this off to the boneyard.
one other place i forgot to mention, is check the K member where the hoses to the rack are clamped. sometimes dirt and rust collect there, finally making it's way through the hoses.
just things i have run into over the years with this model van [bus-my term ] with this engine.
don't know if this is any help or not.