Loud knocking or metallic banging noise from engine during operation

Safety: Stop the engine immediately if a new loud knock develops. Continuing to run can cause catastrophic failure.

• Basic checks: Verify oil level and pressure. Listen with a mechanic’s stethoscope to localize the noise (top end vs bottom end).
• Injector isolation: On mechanical systems, briefly crack injector lines one at a time (if safe) to see if noise changes, indicating a faulty injector.
• Do not overload: Remove load and avoid further operation until inspected.
• Professional diagnosis: Internal engine knocks require teardown and inspection by a Perkins engine specialist.