5 Factors Which Causes Engine Piston Noises

Piston Running Noises Can be Caused by a wide variety of influences during operation of the engine.The Following are the few cause by which Noises occur in Piston Function  :-

Tilting of the Piston due to Excessive Clearance  :-

The piston can tilt if the dimensions of the cylinder bore are too large or as a result of wear / material breakdown, stimulated by the pendulum motion of the connecting rod and the change of bearing surface of the piston in the cylinder, and the piston hits hard against the cylinder  running surface (with the piston crown in particular) as a result.

Tilting of the piston caused by Insufficient clearance in the Piston Pin Bed :-

 The clearance between the piston pin and the small end bush can either be too small by design , or it may have been eliminated by jamming or warping in operation.This can happen particularly as a result of connecting rod misalignment (bending and /or twisting).

Piston Striking in the Direction of the Piston Pin :-

 Any lateral striking of the cylinder bore by the piston mostly stems from the connecting rod.Due to misalignment of the connecting rod (bending or twisting in particular), the piston performs as pendulum movement during its upward /downwards stroke in the longitudinal axis of the engines as a result of which the piston strikes in an alternating sequence against the cylinder. Asymmetric connecting rods or non-concentric support for the piston by the connecting rod have the same effect.

Piston Pin Striking alternately against the Piston pin circlips :-

Axial thrust in the piston pin is always the result of an alignment error between the axis of the piston pin and the crankshaft axis.As described in the previous point, distortion or twisting of the connecting rod and asymmetry of the connecting rod are the mist common cause for this types of fault.However, excessive big-end bearing clearances (Big-end bearing journal on the crankshaft ) can cause a lateral pendulum movement of the connecting rod, particularly  at lower engine  speeds .The Piston pin is skewed as a result in the connecting small end rod and is pushed back and forth in the piston pin bore due to the pendulum motion of the piston.The Piston pin strikes against the piston pin circlips as a consequence. 

The Correct Installation Direction of the Piston was Ignored :-

In order to smoothen the change of the contact surface of the piston before TDC and before the power stroke, the piston pin axis is offset by some tenth of a millimeter towards the piston pressure side.If the Piston is inserted the wrong way round (i.e.. rotated by 180 degree) and therefore the piston pin axis is offset to the wrong direction, then the piston changes bearing surface at the wrong time.The piston titling is then much heavier and much noisier .