Excavator inspection: The "hidden illness" detection method known only to 8 veteran mechanics

June 12, 2026

A routine inspection involves checking the appearance and listening to the sounds, but the real problems often lie beneath the surface. The following 8 tips will help you uncover the hidden flaws of those "cosmetic-level" refurbished devices.
"Hydraulic oil temperature 'start-up test'"
Perform the operation immediately after the cold machine is started. If the hydraulic system shows sluggish response and slow movement, and the oil temperature returns to normal after rising - this indicates severe leakage in the hydraulic pump or main valve, with wear being masked by the low viscosity of the cold oil. Normal performance: The difference in operation between the cold and hot vehicles should not exceed 20%.
2. Rotational braking "slip distance"
After the excavator rotates 90° and then stops abruptly, measure the lateral drift distance of the bucket teeth tip.
Excellent: < 30cm
Caution: 30 - 60 cm
Severe: > 60cm (The steering motor or brake pads have failed)
3. "Road Test Quantification" for Deviation in Movement
Find a 50-meter straight road. Push the left and right walking rods all the way down without correcting the direction.
Within 1 meter off-center: Normal wear and tear
Deviation of 1-2 meters: The walking motor needs to be replaced or adjusted.
Deviated by more than 2 meters: One of the engines is almost completely worn out.
4. Natural descent of the boom "time-lapse monitoring"
Raise the boom to its maximum height, turn off the engine, and record separately:
5-minute subsidence amount: Normal ≤ 10mm
30-minute subsidence amount: Normal ≤ 30mm
If there is no movement for 5 minutes and then a significant drop in pressure within 30 minutes → There is a potential problem with the "lip" of the oil cylinder seal.
5. "Reverse flushing marks" on the radiator
Check if the fins of the radiator have been flushed in reverse (in normal use, dust flows from outside to inside; reverse flushing would leave water stains and tilted fins). Multiple reverse flushings indicate that the machine has been frequently exposed to high temperatures and the radiator has become severely clogged.
6. "Hidden Rust in the Cab"
Remove the floor rubber sheet and inspect the bottom plate for rust. For machines that have been operating in saline soil or coastal areas for a long time, the bottom plate deteriorates from the inside out, and the exterior paint cannot cover up the damage. Use a screwdriver to poke it. If you can penetrate it, immediately give up.
7. Circuit System "Sleep Current"
After turning off the power supply, measure the current from the negative terminal of the battery using a multimeter in series connection.
Normal: < 50mA
Warning: 50 - 150mA (with leakage)
150mA: If the device fails to ignite after being left on for three days, there is a severe short circuit in the wiring or the additional equipment is leaking electricity.
8. "Three Oils" - Identifying Damage by Smell
Engine oil: Has a diesel smell → High-pressure oil pump or injector leakage
Hydraulic oil has a burnt smell → The hydraulic system was exposed to high temperatures, and the pump or valve interior was damaged by burning.
Wear-resistant oil for walking: Has a metallic smell and a grayish color → Severe wear of planetary gears