Water Pump

Thought I'd start a new thread with this one.
I got the engine in the car a couple of days ago and when I put the water in it just came straight out of the water pump. Quite a major leak.

I went out this evening to start the job of changing the pump but just thought I'd confirm the problem first. Filled it up with water, started the engine and ran it for 5 minutes and not a drop of water..

Now, the pump had been off the car for a couple of months so had completely dried out - but why would that make it leak? It seems that now it's soaked for a couple of days it's sealed up again.

Has anyone else had this happen. I'm not quite sure if I should leave it now.

Any thoughts?

if the seal had dried out then water will leak past the seal into the weep hole.
if its not leaking now leave the engine idling for around 15 mins and check for leaks if ok then take it on a run for a couple miles to get system fully pressurised then recheck for leaks
the seal may have swelled and seled now

i had the exact same problem, ordered a new pump. checked the car before starting the work and leak had gone, been fine for the past 12 months