Make sure you do a thorough diagnostic. here's my timeline and mis-diagnosed experience:
1) replaced WP/thermostat
2) coolant leak when cold, puddle in the front on level street, puddle in the back (toward firewall) when park on incline.
3) I said (and so did alot of peopel), damn the VP leaked.
4) so I did the VP, but leak persisted.

it turned out to be 0-rings on coolant pipes going to WP were pinched.

The solution is to reseat the WP, I dremelled three 10mm long lug-nut bolts(cut off the hex head and dremell a slot for small screw driver to turn them in into where the WP bolts go, these become the guide for WP to slide into place, once you secure the rest of original bolts these three will come out and replace by the original bolts if that make sense). Problem solved, I have not top any coolant in 1 year now.

BTW this is on M62 4.4i engine only.