Ford: 87 Crown Vic Strange coolant leak

I have a strange leak coming somewhere around the water
pump.Lower rad hose OK. The leak only seems to appear
when car is not running, mostly overnight. A puddle appears
under water pump area and radiator container needs topping
up. Car can run for 1 or 2 hours and rad level fine.
Any Guesses?

TIA for any Info
Rob

Robert Lynch opined in news:com:
 

Get a light and mirror and check the weep-hole under the pump shaft.

This is not unusual failure mode... the seal is wearing out and it doesnt
show a leak until the engine cools. Running pressure keeps seal seated.

Suggest also change rad cap, the reclaim release valve (center of gasket) may
be sticky making problem worse. But pump is definitely bad if you see
trickle or drops at weep-hole