Previously, I was leaking from the thermostat housing, and not that that's fixed I'm leaking from another place, this time in the far rear / center of the engine which only appears after the car has been sitting for about 8hrs. I'll notice it when I go out to go to work and when I look underneath there's collant on the rear engine cross bar. Looked from the top during lunch today and saw nothing too odd. I'll dig into it this weekend when I have some free time, but in the mean time, what are the likely culprits? Last time I'd begin to see the leak soon after shutting the van off, but this time is different. She runs fine and isn't overheating at all.

TIA,

john