Signs of a Bad Connecting Rod

by William Zane

The connecting rods in your engine are the components that support the piston as it travels up and down inside of the cylinder bore in the block. The connecting rod is fastened around the crankshaft on one end and to the piston on the other end. The ends of the rod spin around the crankshaft and the wrist pin of the piston. As the crankshaft turns, the rod also turns, forcing the piston up and down. A bad rod or rod bearing will eventually destroy an engine.

Knocking Noise From Engine

Listen for a knocking noise when the engine is running. This will likely be worse when the engine is cold and before the oil has had a chance to warm up and begin thoroughly lubricating the components. A rod knock is a hollow sound that speeds up as the engine RPMs rise. The knock may still be there when the car is warm or may go away entirely.

Low Oil Pressure

Check the oil pressure. A bad rod or rod bearing can also cause the oil pressure to be excessively low. Signs of low oil pressure can be an oil pressure light turning on or a low oil pressure reading if the engine has an oil pressure gauge.

Excessive Oil Consumption

Determine if the engine is using excessive oil. If the engine is consistently running low on oil, it may be due to a bad connecting rod or bad connecting rod bearing.

Visual Inspection

The only surefire way to determine if you have a bad connecting rod is to disassemble the engine and examine the connecting rod, the bearings, the piston wrist pin and the crankshaft where the connecting rod bearings slide back and forth. This is obviously an expensive proposition, but a bad connecting rod will require a full engine rebuild anyway.

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