There is a possible issue with the fan. The late fans would move more air than the early ones. About 300 cfm I think, which is about 10% gain over the total amount. If you have gunk in the hose, I would suggest you flush the system. You could have a lot of buildup of rust and minerals previous to this that will affect heat transfer. Also, the heater hose acts as a sort of bypass for the water pump. Circulating the coolant through it will help with keeping an even temp.