85 Chevy 350 Conversion Van Overheats):

Since it has been messed with in the accessories drive belts, one possibility is the remaining belt was improperly routed and is now spinning the water pump backwards. If has a flat serpentine belt, it can be done. V- belt not so e-z but some idiots are very resourceful.

If there is not a belt routing diagram sticker under the hood, see if you can find a proper diagram in a service manual.

Best of luck!