How to troubleshoot engine overheat in Audi 80?

My Audi 80's engine keeps overheating, even after I've replaced the coolant and checked the thermostat. What could be causing it?

First, make sure that there are no leaks in the cooling system. Even a small leak can cause the engine to overheat. Also, check the radiator and make sure it is not clogged. If everything looks fine, it could be an issue with the water pump or a faulty temperature sensor. My advice would be to take your car to a reputable mechanic for a thorough diagnosis.