motor overheating

Hi-- One of my dehumidifiers, a Sears model that's about 10 years old, gets very hot when it runs. I believe it's the fan motor, not the compressor motor, that heats up. The plug gets hot as well. I've oiled the motor, but that had no effect. The humidifier functions fine, but it definitely gets hotter than it should. Any ideas on what could be causing this, and what I could do about it? Thanks in advance... Eric