We use two steps: 1. Insert a medical-grade endoscope through the spark plug hole to visually inspect cylinder wall scratches and carbon buildup on the piston top; 2. Extract an engine oil sample to check for large metal debris or emulsification (caused by coolant leakage).

We maintain an absolute skeptical attitude. In addition to regular visual inspections, we focus on checking for sediment accumulation around the sunroof drainage channels and look for water stains under the A-pillar trim and front floor mats. This is the only effective physical evidence to determine if the sunroof drainage holes are blocked, leading to hidden leaks.

It's extremely difficult. The security level of Chinese brand immobilizers is very high, and you must connect a specialized factory computer to the vehicle's OBD and be online with the domestic server to match it. Losing all keys usually means you need to replace the entire lock cylinder and anti-theft control module while overseas.