Heating Element
A defective heating element can make a dryer too hot. If the element partially shorts out, it can produce heat all the time, regardless of whether the dryer is calling for heat. Remove the heating element to inspect it. The coils should not be touching each other or anything else.
Other Causes and Conditions
Air Flow Problem
Dryers need good ventilation to work properly. If the vent is clogged it can make the dryer too hot. Clean all of the vent tubing thoroughly.
Cycling Thermostat
Although not common, a defective cycling thermostat can make the dryer too hot. The cycling thermostat is supposed to turn on and off the heat to maintain the proper temperature. If the thermostat is defective it may keep the heat on too long. The thermostat is not adjustable or repairable, it must be replaced.
Felt Seal
Most dryers have a felt seal at the front and rear of the drum to keep the heat inside the drum. If the felt seal is worn away or missing, the dryer may keep heating and make the dryer too hot. This is not common.
Blower Wheel
A defective blower wheel will not spin properly and will not vent the hot air, making the dryer too hot. Check to see if there is adequate airflow out of the dryer.