I am reporting a severe defect in my 2020 Audi Q7 involving aœcoolant migrationa due to a faulty water pump, a known issue in Audi models (Q7, S4, A6, 2013a“2022). This poses critical safety risks due to sudden failure with minimal warning. My out-of-warranty Q7 showed minor coolant fouling near a solenoid, with normal coolant levels and no fluid added. The dealer quoted ~$6,000 to replace the water pump and vacuum system. This defect is highly dangerous due to: Sudden Power Loss: Coolant in the vacuum system impairs solenoids and lines, disrupting engine/turbo function. This can cause abrupt power loss, risking loss of control in traffic or at high speeds, potentially leading to collisions. Catastrophic Overheating: A failing water pump may halt coolant circulation, causing rapid engine overheating without warning, risking sudden engine shutdown and stranding drivers in hazardous conditions like highways. Brake Assist Failure: The vacuum system powers the brake booster. Contamination can reduce braking effectiveness, increasing pedal effort and stopping distances, heightening collision risks in emergencies. Emissions Control Issues: Coolant fouling affects PCV and EVAP systems, causing misfires, stalling, or increased emissions, potentially triggering check engine lights and compromising engine stability. Undetectable Progression: The defect often shows no clear symptoms or warnings until severe damage occurs. My vehicle had only minor fouling that could only be detected by visual inspection, yet extensive repairs were needed, indicating the issueas stealthy nature, which prevents timely driver intervention. Systemic Issue: Forums and a class-action lawsuit confirm this defect across Audi models, yet owners face high repair costs post-warranty. This defect endangers drivers and others by risking vehicle failure, impaired braking, and unstable performance. I urge NHTSA to investigate and mandate a recall or extended warranty.