A dryer, like all appliances, needs regular maintenance to keep it in good working order. However, a well-maintained dryer may still have problems every now and then. A dryer that is overheating is a hazard that needs to be immediately taken care of. Overheating can easily damage the dryer and, more seriously, it is a fire hazard. One indication of an overheating problem is the temperature of the clothes when they come out of the dryer. Clothes should feel warm at the end of the drying cycle. If they are too hot to hold comfortably, the dryer is probably overheating. If the dryer is overheating, don't use it until you have corrected the problem.
Check the lint trap. The lint trap works as a filter and it should be emptied out each time before the dryer is used. If it is clogged with lint, this may be why the dryer is overheating.
Examine the vent duct. The vent duct goes from the back of the dryer to the outside and it allows the heat from the dryer to exit outside the house. A common problem is lint that becomes stuck in the vent duct forming a blockage. Another common problem is a kink in the duct. This often occurs when the dryer is moved or pushed too close to the wall. Place the dryer 12 inches from the the wall for proper ventilation. If you don't find any blockage or kinks in the vent duct inside the house, inspect the outside where the vent exits the exterior wall. It may be blocked or kinked on the outside.
Inspect the internal duct work. Dryers also have an internal duct work system that can become clogged with lint. This is more complicated and may require a professional repairman. However, before calling a professional, try fixing the problem with a vacuum cleaner. Remove the lint trap and inspect the inside duct with a flashlight. You may see the blockage. Use a vacuum cleaner to clean out the duct. If the dryer is still overheating, the internal duct may be clogged beyond what the vacuum cleaner can reach or the thermostat may be faulty.
Test the cycling thermostat. It is rare for a faulty cycling thermostat to cause a dryer to overheat, but it is a possible source of the problem. The cycling thermostat is a small, round, black device that is mounted to an oblong steel plate that is usually mounted to the internal duct with two screws. Remove the thermostat and take it to the local hardware store, where you can have it tested to determine if it is good or bad. If the thermostat is bad, replace it with a new one. If the thermostat is good, reattach to its proper place in the dryer.
Call a professional repairman.