A clunking abnormal noise at the articulation points of an excavator is often caused by excessive clearance due to bushing wear. Blind replacement may result in unnecessary costs, and the correct diagnosis should follow the procedure below:

Step 1: Shut down the machine to release stress and locate the noise source

Place the working device steadily on the ground and relieve the pressure of the hydraulic system. Wiggle the articulation points of the boom, arm and bucket one by one to pinpoint the exact location of the noise.

Step 2: Measure the key clearance (core diagnosis)

Use a crowbar or jack to lift the relevant components, simulating the stress state of the pin shaft during actual operation. Then directly measure the radial clearance between the pin shaft and the bushing with a feeler gauge, or measure the relative displacement on both sides of the structural component. Refer to the specifications in the maintenance manual (the limit value is usually 1-2 mm); if the measured clearance exceeds the standard by more than 50%, the bushing wear can be determined as the primary cause.

Step 3: Eliminate "false" abnormal noise

Inspect and rule out the following potential causes:

• Insufficient lubrication: Check if the abnormal noise disappears temporarily after applying grease to the articulation point.

• Pin shaft wear: Inspect the surface of the pin shaft for step-like wear or scuffing.

• Structural component cracking: Carefully check the weld seams and base material of the ear plates for cracks.

Step 4: Concomitant inspection and decision-making

If excessive bushing clearance is confirmed:

1. The corresponding pin shaft must be inspected simultaneously and replaced together if its wear exceeds the standard.

2. Check if the bushing housing bore is out-of-round and rectify it if necessary.

3. Replace the bushings on both sides of the same articulation point in pairs to ensure even force distribution.

Following the "location → measurement → elimination → decision-making" procedure can accurately identify the root cause of the abnormal noise and avoid misreplacing parts. Data shows that more than 30% of bushing-induced abnormal noises are accompanied by pin shaft wear; only simultaneous replacement of both parts can truly eradicate the problem and save long-term maintenance costs.