1989 Oldsmobile Cutlass Overheating Problem

Engine Cooling problem
1989 Oldsmobile Cutlass Front Wheel Drive Automatic 57000 miles

I have a 1989 Oldsmobile Cutlass Ciera. My coolant system is full, radiator and overflow tank. I have no leakages in the radiator, pipes, tank, nor the heating coil. No coolant is being lost at any noticable rate. Yet my engine temperatures are continually redlining, and often there is no hot air blowing out of either the heater or the defroster. I'm confused and wonder if this is a thermostat, water pump or other problem.