Cleanliness is the difference between a rough idle and a smooth-running N14. Learn the professional procedure for using the M20139 copper brush.

The Danger of Improper Bore Cleaning

Many technicians reach for a standard steel wire brush to clean injector bores, but this is a critical mistake. Steel is harder than the cast iron or aluminum of the cylinder head; it can score the sealing shoulder, creating a path for fuel or air leaks that a new copper washer can't fill. The M20139 uses copper bristles specifically because they are softer than the head material.

The 5-Step Cummins Bore Prep

1. Debris Check: Use a shop vacuum to pull out any loose flakes before inserting the brush.
2. Tool Setup: Secure the M20139 in a variable-speed drill or a comfortable hand driver.
3. Low-RPM Scrub: If using a drill, keep it on the lowest setting. Insert the brush and apply light downward pressure to the seat area.
4. Visual Inspection: Use a bright light to ensure the bottom "ring" of the bore is shiny and free of carbon rings.
5. Final Flush: Use a lint-free swab and a light solvent to remove any remaining copper dust or residue.

Why Shop Owners Trust Apex

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