2001 Oldsmobile Aurora Leak in Coolant Surge Tank?

Engine Cooling problem
2001 Oldsmobile Aurora Two Wheel Drive Automatic 32000 miles

Have a leak not sure where it's located. Could be under, on the side, along the hoses, not sure. A pressure test was done no leak found. Coolant leaks on the floor often. Sometimes a little and other times alot. Doesn't look like a crack in tank. Please advise. I did donate $5.00