Cummins ISX11.9 CM2250 – Service Manual 001-043   Piston

• Remove and disassemble the piston and connecting rod assemblies. Refer to Procedure 001-054 in Section 1.

WARNING  When using solvents, acids, or alkaline materials for cleaning, follow the manufacturer’s recommendations for use. Wear goggles and protective clothing to reduce the possibility of personal injury.

CAUTION  To reduce the possibility of damage to the piston, the cleaning solvent must be approved for bushing material. If necessary, brush the pistons with a soft non-metallic brush. A metallic brush can damage the piston ring grooves.

It is only necessary to remove the carbon buildup. It is not necessary to make the crown appear to be new.

CAUTION  When using walnut shell blast to clean steel pistons, use the minimum recommended pressure and do not concentrate the blast in any one area for extended lengths of time. To prevent damage of the surface finish, make sure the pin bore area is protected from the blast. Oil galleries should be masked when using blast media to clean pistons.

Do not use glass or plastic bead media to clean the piston crowns.

Carbon deposits can be cleaned from the pistons by soaking in an approved solution and/or by blasting with walnut shell media.

NOTE: Piston skirts should be masked or protected when using blasting media, to prevent damage to the surface finish.

Soak steel pistons for at least 30 minutes in an approved cleaning solvent for steel and for bushing material. Use a hot, soapy solution with a non-metallic brush to remove carbon deposits.

For best results, soak the pistons several hours or overnight.

WARNING  When using a steam cleaner, wear safety glasses or a face shield as well as protective clothing. Hot steam can cause serious personal injury.

WARNING  Wear appropriate eye and face protection when using compressed air. Flying debris and dirt can cause personal injury.

Use steam to clean the pistons.

Dry with compressed air.

CAUTION  Do not use pistons with cracks. If the skirt is cracked, it must be replaced. Failure to replace the damaged piston can cause serious engine damage.

Inspect the piston bowl for cracks or other damage.

Inspect the piston pin bore for cracks, scratches, galling, dents, or other damage.

If significant damage is found, the piston must be replaced.

Inspect the piston second ring land for scuffing. Refer to Single Piece, Open Skirt Piston Reuse Guidelines, Bulletin 4021925.

Inspect the skirt for scratches. In general, if the scratches can be felt with a fingernail, do not reuse the piston. Refer to Guidelines for Single Piece, Open Skirt Piston Reuse Guidelines, Bulletin 4021925, if additional information is needed.

The ring groove can be inspected with a new ring and a feeler gauge.

Hold a new ring in the groove, even with the outside diameter of the piston.

Install a 0.15-mm [0.006-in] feeler gauge.

If the feeler gauge enters the groove without resistance, replace the piston.

Measure the piston pin bore inside diameter.

Piston Pin Bore Inside Diameter

NOTE: The piston pin bore has a trumpet shape, which increases the pin bore diameter at the inner and outer edges. Measurements should be taken at the smallest part of the piston pin bore.

Inspect the piston pin for scratches, grooves, or other damage. Do not reuse if visually unacceptable.

Measure the piston pin outside diameter.

Piston Pin Outside Diameter

Piston Pin Length

• Assemble and install the piston and connecting rod assembly. Refer to Procedure 001-054 in Section 1.
• Operate the engine to normal operating temperature and check for proper operation.