What common issue causes the Audi 80's engine to overheat?

I recently bought a used Audi 80 and after a few drives, I noticed that the engine temperature gauge would climb higher than normal. What could be causing this issue and how can I fix it?

One common issue that can cause an Audi 80's engine to overheat is a faulty thermostat. It regulates the engine's temperature and if it is stuck closed, it can prevent proper cooling. It is a relatively easy and inexpensive fix, so it's worth checking first before diving into more complex solutions.