Anything is possible, but water pumps usually fail when bearing failure leads to seal failure which results in a leak. The business end of the water pump is a simple impeller that spins, so about the only thing that could happen would be disintegration of the impeller due to rust or perhaps it getting loose and spinning on the shaft (I've never seen either). To determine overheating you will need a working temperature gauge or have a way to measure temperature. Engine coolant can also be forced out if combustion gasses are entering cooling system (resembles a boil-over). If you think this may be happening I'd use a
sniffer to check for combustion gasses here. Overheating issues with these vans can be caused by aftermarket thermostats. There are several that will fit, but do not work well. I've experienced this 1st hand and as a result will now only use the OEM t-stats that are listed by application for the van.
FYI, The heater system on the van bypasses the thermostat. The heater hose circuit gets full flow regardless of t-stat position. If your coolant is hot and there's no restriction in the heater system, then your heater hoses must get hot. I guess it's possible you have an air bubble in the system causing cavitation, but those will typically only interfere temporarily and clear themselves after a single heat/cool cycle. If you've ruled that out, verified there's no combustion gasses in the cooling system, and verified t-stat is good (and OEM) then the next logical step is to pull the pump. Tim