So a few weeks back I noticed some coolant had leaked from the van as per a
6" diameter coolant stain in the parking stall under the motor (2.1
digifant - 1986).  I noticed that the coolant had been dripping from what
appears to be the bottom of the water pump - however I can't confirm this
as the oil cooler obstructs my view from looking directly at the water
pump.  (Water pump replaced approx 15k miles ago)

Anyway I drove the van basically to work and back for a few weeks (short
trips) and the leak seemed to go away - no drips.  What I have noticed
since this time is that once I get the engine warmed up to normal operating
temp the dripping coolant returns - leaking out from up and between the oil
cooler and oil pressure relief valve.  Looking down at the engine through
the engine bay and with a good light - there is nothing to see leaking
either.

My short trips to work don't get the vehicle up to normal operating
temperatures so this dripping doesn't happen that much - and the amount of
coolant typically lost is about 1/4 cup.

Any thoughts on what might be creating this?

Thanks,

Bruce