So I purchased a 1996 Audi A6 2.8 Quattro. The motor was rebuilt at 200k. It’s got about 225k on it now. I have been having issues with it overheating. It seems to me that once the engine gets hot the fans will not kick on for cooling. This causes my coolant tank to begin steaming and spewing coolant. I have already replaced the fans and fan switch and they work when I turn the AC on. I have also replaced the coolant sensor and switch today. At the same time I bled any air out of the coolant tubes. I have ran the car until the fans should have surely came on but still won’t without forcing them by turning on AC. I’m trying to avoid replacing the T-stat and water pump if not necessary. What else could be causing the issue??? Please help!!