Centinel System – Repair Manual – 001-043   Piston

Some Signature, ISX, and QSX15 engines are equipped with articulated pistons.

The articulated piston is a two-piece piston consisting of a forged steel crown and an aluminum skirt.

An open chamber oil gallery is located on the underside of the crown of the piston to provide more oil contact with the piston and give better piston cooling. Piston cooling nozzle targeting is critical because the oil is captured in shaker trays.

Some engines are equipped with single-piece pistons.

The single-piece piston is a one-piece piston, that does
not have a bushing and is forged from a high-strength, alloy steel.

A cover plate, that is
not removable, is located on the underside of the piston to capture oil and cool the piston.

Do
not remove this cover plate under any circumstances.

Remove the piston and connecting rod assemblies from the engine.
Refer to Procedure 001-054 (Piston and Connecting Rod Assembly) in Section 1.

Disassemble the piston and connecting rod assembly.
Refer to Procedure 001-054 (Piston and Connecting Rod Assembly) 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 crown, the cleaning solvent must be approved for bushing material. If necessary, brush the piston crowns 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 piston crowns, use the minimum recommended pressure and do not concentrate the blast in any one area for extended lengths of time. Make sure the pin bore area is protected from the blast so as not to damage the surface finish. Do not use walnut shell blast to clean aluminum piston skirts.

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

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

Soak steel pistons for at least 30 minutes in an approved cleaning solvent for steel and for brushing 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 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  If necessary, brush the piston crowns with a soft non-metallic brush. A metallic brush can damage the surface finish. Do not use glass, plastic, or walnut media to clean the aluminum piston skirts. This can damage the pin bore surface finish or prevent the rings from seating correctly in the ring grooves.

Soak aluminum pistons for a minimum of 30 minutes in a tank containing an approved cleaning solvent for aluminum. Use a hot soapy solution with a non-metallic brush to remove carbon deposits. Anything more abrasive will damage the surface finish.

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

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

Use steam to clean the pistons.

Dry with compressed air.

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.

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.

Soak steel pistons for at least 30 minutes in an approved cleaning solvent for steel and for brushing 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  Wear appropriate eye and face protection when using compressed air. Flying debris and dirt can cause bodily injury.

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

Use steam to clean the pistons.

Dry with compressed air.

Make certain there is
not walnut shell blast media remaining between the oil cover plate and the piston.

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

Inspect the piston bowl for cracks or damage.

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

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

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 skirt pin bore (1) and sides (2) for cracks or damage.

Also inspect the skirt for scratches. In general, if the scratches can be felt with a fingernail, do
not reuse the skirts.
Refer to Articulated Piston Skirt Reuse Guidelines for Signature, ISX, and QSX15 Engines, Service Bulletin 4021468, 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, there is too much wear. Replace the piston.

Measure the piston pin bore inside diameter on both the crown and skirt on articulated pistons.

The piston pin bore inside diameter is
not a re-use criteria measurement to be taken on single-piece pistons.

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 diameters are the same between articulated and single-piece piston pins.

Also measure the piston pin lengths. Single-piece piston pins are shorter than articulated piston pins.

Assemble the piston and connecting rod.
Refer to Procedure 001-054 (Piston and Connecting Rod Assembly) in Section 1.

Install the piston and connecting rod assembly.
Refer to Procedure 001-054 (Piston and Connecting Rod Assembly) in Section 1.

If failure resulted in coolant, oil, excessive fuel or excessive black smoke entering the exhaust system, the aftertreatment system
must be inspected.
Refer to Procedure 014-013 (Aftertreatment Testing) in Section 14.