dryer keeps over heating & cutting out?

Hi i have a white knight 44w tumble dryer and it started to get very hot on high heat and kept cutting out after 5 mins, now i thought straight away it must be a thermostat of some kind so i looked into it and changed the exhaust and inlet thermostats but it still keeps ove heating i can run it on low heat setting and it doesn't cut out but have noticed the heat is a lot higher than it normally is on low. Please can somebody help me out with the solution. thank you Gray.