We thoroughly rule them out by checking if the cabin wiring harness is melted, if the seat belts have water stains or mold, if there is unusual rust or debris in the seat tracks and cigarette lighter, and by verifying with the insurance company for any "total loss claims." These two types of cars are an absolute sales ban for us.

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).

The lifespan of rubber sealing strips for frameless doors is usually only 4-5 years. We carefully press the sealing strip at the edge of the roof to check for loss of elasticity and use a high-pressure water gun to wash the seams of the windows to check for direct water leakage due to aging.