When sourcing a secondhand excavator, you must prioritize the engine condition and hydraulic system performance. Check the operating hours; typically, machines with under 5,000 to 8,000 hours offer the best balance of price and remaining service life. Inspect the main pump pressure and look for signs of hydraulic oil leaks or contamination. Additionally, evaluate the undercarriage wear (tracks, rollers, and idlers), as replacing these components can cost up to 20% of the machine's value. Ensure the boom and arm have no structural cracks or excessive welding repairs.