Chevrolet Repair: no heat in 1991 chevy c1500 pickup, chevy c1500, core leak

Question
I have no heat in my chevy 1991 c1500 pickup.  thermostat goes to operating temp ok. have replaced heater core.  line in to heater core gets hot but not real hot line out does not get very hot. any suggestions?  thanks cal

Answer
Sounds like your heater core has low flow.  YOu will want to take those hoses loose and flush water through the core with a garden hose and compressed air if you have access.  Be prepared this may free up enough junk to cause a heater core leak and then you will have to replace it.