On Digijet vans the = thermostat housing and all the connections in that area are real suspect as = well. If not the expansion tank, take a look adjacent there at where the cover = over the thermostat bolts to its housing, where the housing bolts to the water = pump (that gasket really tends to leak if not a new honest VW style gasket with = foam core and graffoil sides) the o-ring on the cross pipe at that location into = the thermostat housing and the other gasket from thermostat housing to the = pipe stub that goes to the head. I count at LEAST 11 joints all in that = immediate vicinity between gaskets, hose connections, and O-rings, not even = counting the water pump O-ring or connections to the expansion tank. And the = weep hole on the water pump in the bizzare chance the belt was WAY to tight or you = had a defective pump.

Don't sweat the heads = so much yet, there are a lot of places to drip round there, I will give the = late vans a credit for a somewhat better design in this area. If I had to make = a guess though, I'll guess the housing to water pump gasket or the O-ring on the = thermostat itself as its cover deforms and both those locations are = clamped by long spindly 6mm bolts and both surfaces tend to warp.