heater in 2010 escape blpws cold when idling

2010 FORD ESCAPE, blows cold air unless rpm is at 2500-3000. Once engine is warm the supply heater hose is at 165 degrees and the return hose is at 85 degrees. run rpm up and both are at 160. this is what it doing when I began this project. Initial problem was low coolant. I found the water pump leaking at the weep hole and t-stat housing was cracked. Replaced both and still same problem. been through several warm up/cool downs and its not taking anymore coolant.