96 E150 No Flow through Heater Core

I have a 96 E150. I have no hot water flowing through the heater core. I removed and cleaned the core. It flows well out of the van. Reinstalled in the van and still get no flow. Any ideas?

Worn waterpump?
Did you feel the heater hoses going to the core after the motor is warmed up? Are they hot? Is the blend door opening and closing?

I"m going with the water pump. I just bought the van, It doesn't over heat, but with the cold weather, it may not. Can't come up with any other reason for no heat to the core. Thanks

Did you feel the heater hoses? Flow may seem good through the core when out of the car, but it maybe still restricted.

the suggestions by other members are very likely and also good places to start but it could possible be the heater control valve.