Just wanted to share a tip for tracking slow coolant leaks...  Often,
the heat from running the van will evaporate small leaks without a
trace, but if you get a cooling system pressure test kit (Autozone
loan-a-tool, etc.), you can keep the system pressurized while cold
(say for a few hours), and those small leaks will stay visible.

-Alex (who sees some stainless cooling tubes and an upgrade to a
late-model radiator in his future)