B5.9G, B5.9LPG – Troubleshooting and Repair Manual – 001-014   Connecting Rod

Improper maintenance of the lubrication system is also the primary cause of reduced main bearing life.

A malfunction of the crankshaft/main bearing will usually be detected by reduced lubricating oil pressure. If the rod bearings continue operation with low-lubricating oil pressure, this will lead to a rapid deterioration of the bearings and eventually will produce a knocking sound.

A connecting rod knock occurs when the engine is not loaded. Verify by first applying load and then unloading and listening for the knock.

WARNING  Coolant is toxic. Keep away from children and pets. If not reused, dispose of in accordance with local environmental regulations.

WARNING  Do not remove the pressure cap from a hot engine. Wait until the coolant temperature is below 50°C [120°F] before removing the pressure cap. Heated coolant spray or steam can cause personal injury.

Drain the coolant. Refer to Procedure 008-018.

Remove the cylinder head and gasket. Refer to Procedure 002-004.

WARNING  To reduce the possibility of personal injury, avoid direct contact of hot oil with your skin.

WARNING  Some state and federal agencies have determined that used engine oil can be carcinogenic and cause reproductive toxicity. Avoid inhalation of vapors, ingestion, and prolonged contact with used engine oil. If not reused, dispose of in accordance with local environmental regulations.

Drain the lubricating oil. Refer to Procedure 007-025.

Remove the lubricating oil pan and gasket. Refer to Procedure 007-025.

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

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  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  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.

Use steam or solvent to clean the connecting rods.

Dry with compressed air.

Inspect the connecting rods and connecting rod caps for damage.

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

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

Measure the connecting rod piston pin bushing inside diameter.

Measure the connecting rod crank bore with the bearing shells removed and the capscrews tightened.

If the connecting rod crank-end bore measurements are not
within specifications, replace the rod assembly.

Measure the connecting rod crankshaft bore inside diameter with the bearings installed. Verify the torque of the capscrews.

Measure the diameter of the rod journal on the crankshaft.

NOTE: If crankshaft rod journals are not within the given specifications, the crankshaft must be removed and reground.

Bearing clearance equals rod inside diameter (with bearing) (1) minus the crankshaft journal diameter (2).

Bearing clearance can also be determined with Plastigauge during engine assembly.

Install the pistons and connecting rod assemblies. Refer to Procedure
001-054.

Install lubricating oil pan and gasket. Refer to Procedure 007-025.

Install the cylinder head. Refer to Procedure 002-004.

WARNING  Some state and federal agencies have determined that used engine oil can be carcinogenic and cause reproductive toxicity. Avoid inhalation of vapors, ingestion, and prolonged contact with used engine oil. If not reused, dispose of in accordance with local environmental regulations.

WARNING  To reduce the possibility of personal injury, avoid direct contact of hot oil with your skin.

Fill the engine with clean gas engine lubricating oil. Refer to Section 7 for the correct lubrication oil specification.

Fill the cooling system. Refer to Procedure 008-018.

Operate the engine to normal operating temperature, and check for leaks.