what causes crankshaft knock
Internal Mechanical Problems. 1  Internal mechanical problems can also cause engine knocking. One such problem stems from excessive clearance inside the bearings in the connecting rods that transfer the downward movement of the pistons to crankshaft rotation. Each time the piston changes direction, there is a knock from the metal hitting metal. This is often referred to as a rod knock. It is usually very rhythmicâit increases with engine speed and intensifies with engine load. Other mechanical problems that lead to engine knocking are: Defective main crankshaft bearings
If the situation is really bad it can even be caused by the rod itself contacting the crankshaft journal (where the bearing has become out of place). The most common cause of rod knock is due to a spun bearing (bearing itself actually spins in the end of the rod so it becomes out of position).