2018 AUDI A5 Engine And Engine Cooling Problems

I own a 2018 Audi A5. Many critical cooling system parts — including the thermostat housing, water pump housing, radiator end tanks, breather tubes, and quick-connect hoses — are made of plastic and sit in constant exposure to coolant temperatures over 200°F. Over time, these components become brittle, crack, and fail prematurely. Recently, the plastic breather/return hose between the coolant reservoir and the radiator broke apart during routine service due to brittleness. When these parts fail, coolant leaks quickly, which can cause sudden overheating, engine damage, and potential vehicle disablement while driving. Based on owner reports and my own experience, this appears to be a widespread issue across Audi/VW vehicles of this generation. I request that NHTSA investigate whether the use of plastic in these high-heat, high-pressure components represents a design defect that creates a safety hazard.