You will doubtedly find this to be just water/condensation in the exhaust, check the water in the radiator/header tank, if all is well, take the van on a run, tickover is not sufficient and will just add to the condensation, you should avoid over reving the engine untill its up to running temp, it would be a safe bet to change the oil after a stationary period. Allways keep a time life on the cam belt.
Norman Watts, September 2007