Why does my Audi 80's engine keeps overheating?

I recently purchased a used Audi 80 and noticed that the engine temperature is constantly reaching critical levels. I've checked the coolant levels and they seem to be fine. What could be causing this issue?

The most common cause of an overheating engine in an Audi 80 is a faulty thermostat. It is responsible for regulating the flow of coolant into the engine. I would recommend getting it checked and replaced if necessary.