Hello everyone, I have a 1989 Blue Bird with 5.9 cummins. Took out both heaters and reconnected coolant lines. Turned on bus and no leaks so good there. Now my front heater and defrost aren't getting warm. I let bus run for awhile and the radiator where you fill it wasn't even warm. I live in Montana and it was 28 degrees. Any ideas what I need to do or what I did wrong? Coolant in radiator is near top but not full. Thanks for any help. I also took out the heater pump that was near my 2 back heaters when I took them out. Valve is open. Also seems to be little knocking noise where front air comes out.