NHTSA Complaint #11700476 — 2023 HYUNDAI SONATA

I am reporting a serious coolant system defect on my 2023 Hyundai Sonata Hybrid with about 13,500 miles. The vehicle develops an internal coolant leak while driving. Coolant burns off and white steam/smoke comes out of the exhaust, especially during acceleration. When this happens, the coolant level drops quickly, the interior heater stops working, and the car soon displays an engine overheating warning, forcing me to stop driving. This has happened multiple times and makes the vehicle unsafe. When I checked under the hood, coolant was at a low/empty level after overheating events. The car becomes undriveable once the alarm appears. I took the vehicle to a Hyundai dealer, and even though the vehicle is only 2 years old, they told me it was “out of warranty.” I had to pay about $1,500 for repairs, and since the dealer refused a loaner, I paid $250 for a rental car. I called Hyundai USA on 9/13/2025 and opened Case Number XXX. Hyundai acknowledged they are aware of coolant issues on the Sonata Hybrid but said no recall exists. This issue appears widespread. Many other owners report the same symptoms: white exhaust steam, coolant smell, coolant loss, no interior heat, and engine overheating. Hyundai released TSB 23-EM-009H, describing a failure where coolant leaks internally in the Exhaust Heat Recovery System (EHRS), causing white smoke and overheating—matching my symptoms exactly. This defect is a safety hazard because overheating can occur suddenly while driving, risking engine damage or breakdown in traffic. I request NHTSA investigate this issue as a potential recall-level defect on the 2023 Sonata Hybrid. INFORMATION REDACTED PURSUANT TO THE FREEDOM OF INFORMATION ACT (FOIA), 5 U.S.C. 552(B)(6)