NHTSA Complaint #11690045 — 2020 TOYOTA HIGHLANDER

On September 2, 2025, the vehicle’s Hybrid System shut down on cold start and the vehicle would not start. A dealer inspection reported coolant had entered cylinder #4, allegedly causing the engine block to warp, the cylinder head to crack, and the head gasket to fail. This was a sudden catastrophic engine failure on a five-year-old vehicle with no prior overheating warnings, no dashboard alerts, and no performance issues in the days leading up to the failure. It is highly unlikely for an engine block to warp without sustained overheating, yet the failure occurred on a cold start. The dealership itself described this as a “premature failure” in their service report. At approximately 26,000 miles, the vehicle’s coolant thermostat failed and was replaced under warranty. If the thermostat stuck closed even briefly, the engine could have experienced one or more silent overheat events that never registered on the dashboard. In aluminum blocks, even short bursts of high localized heat can create latent distortion that doesn’t cause immediate problems but can eventually lead to catastrophic failure years later. Safety Risk: – Vehicle became disabled suddenly without warning. – Engine failure occurred without overheating symptoms, creating risk of sudden shutdown during use. Problem Confirmation: – Engine failure confirmed by a Toyota-authorized dealer. – Dealer service report explicitly called this a “premature failure.” Warning Lamps / Symptoms: – A check engine light appeared briefly three days before failure, then cleared on its own. – No overheating warnings or drivability issues were observed prior to failure.