[rwood13]

sounds like an idler pully (pully that does not connect to anything, provides tension on the belt) is going bad, alternator going bad, power steering pump going bad, go to the parts store, get an automotive stethascope and a manual on the van, while the noise is there use the stethascope to find what part the noise is coming from (CAUTION!!! do not get caught in a moving part), use the manual to determine which part is bad