Cummins N14 STC, Celect, Celect Plus – Service Manual 001-014   Connecting Rod

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

NOTE: The piston and connecting rod assemblies must be installed in the same cylinder number from which they were removed, to make sure there is a correct fit of worn mating surfaces if parts are used again.

Use a tag to mark the cylinder number from which each piston and rod assembly was removed.

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.

WARNING  Some solvents are flammable and toxic. Read the manufacturer’s instructions before using.

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 a nylon bristle brush to clean the oil drillings.

Steam clean or use solvent to clean the connecting rods.

Dry with compressed air.

Inspect the rods and the caps for damage.

Replace the rod if the “I-beam” is nicked or damaged.

Inspect the connecting rod and the cap for fretting damage on the mating surfaces.

The rod and the cap must be replaced as an assembly if any fretting damage is visible on either piece.

Inspect the rod pin bore bushing for damage or misalignment of the oil passage and the bushing.

Replace any piston pin bushing that has evidence of scoring, galling, or scuffing. Replace any bushing that has turned.

Special tools and precision machining are required to replace bushings. If Cummins® approved tools and procedures are not available, the connecting rod must be replaced.

CAUTION  The rod cap alpha characters must match the alpha characters on the connecting rod and must be installed with the characters aligned to prevent damage to the connecting rods and crankshaft.

Install the connecting rod caps and the capscrews. Refer to Procedure 001-047 in Section 1.

Measure the rod crankshaft bore inside diameter.

Connecting Rod Crankshaft Bore (Inside Diameter)

If any of the measurements are not within the specifications, the rod must be repaired or replaced.

Measure the piston pin bushing inside diameter.

Piston Pin Bushing (Inside Diameter)

If any of the measurements are not within the specifications, the rod must be repaired or replaced.

The bushing must be precision machined after installation. If machining capability is available, the bushing can be replaced. Refer to the Alternative Repair Manual, Bulletin 3379035.

Remove the capscrews and the rod caps.

Measure the connecting rod capscrew outside diameter.

Connecting Rod Capscrew (Outside Diameter)

Use a connecting rod checking fixture, Part Number ST-561, and a connecting rod mandrel set, Part Number 3823785, to inspect the bend and twist of the rods.

Calibrate the checking fixture with a new rod that has been measured for correct center to center length, 304.75 mm to 304.80 mm [11.998 in to 12.000 in].

NOTE: Assemble the connecting cap to the rod.

Install the piston pin mandrel from the connecting rod mandrel set, Part Number 3823785, into the piston pin bore.

NOTE: Use a mandrel, Part Number 3823787, if the piston pin bushing has been removed or the mandrel, Part Number 3823788, if the bushing is still in place.

Install the mandrel, Part Number 3823785, into the crankshaft bore and expand the mandrel.

NOTE: Make sure the pin on the mandrel is pointed down and locked in position in the center of the connecting rod.

Install the connecting rod into the fixture.

Move the dial holder to position the contact points of the indicators on the mandrel in the piston pin bore.

Tighten the bracket to hold the indicators in position.

Set the dial indicators to read “0”.

Remove the connecting rod from the fixture.

Turn the rod 180 degrees horizontally, and install the rod into the fixture again.

Check the dial indicators for the “0” position again.

If the dial indicators show any change from “0”, adjust the dials to half the indicated reading.

The fixture is now calibrated to allow the connecting rod to be installed into the fixture in either direction, and the dials will indicate an equal deflection on either side of “0”.

Install the mandrel and arbor into the connecting rod to be inspected.

Install the connecting rod into the fixture.

Measure the rod length and bend (alignment).

Connecting Rod Length

Connecting Rod Alignment

Using a feeler gauge, check the clearance between the mandrel and the dial indicator holding plate as illustrated.

Connecting Rod Twist

NOTE: The piston and connecting rod assemblies must be installed in the same cylinder number from which they were removed, to make sure there is a correct fit of worn mating surfaces if parts are used again.

Install the piston and connecting rod assembly. Refer to Procedure 001-054 in Section 1.