Checking the condition of the connecting rod and piston group by ear (Skoda Felicia)

1. If the connecting rod and piston group is in good condition, the engine runs quietly, and at idle speed the oil pressure in the lubrication system does not fall below the permissible limit.

2. Piston knocking occurs when pistons hit the cylinder liner walls due to excessively loose fit. Piston play manifests itself in the form of dull blows and occurs mainly when engine loads increase or when a cold engine is idling. The intensity of the knocking may decrease as the engine warms up, until it disappears completely.

3. Piston pin knocking also occurs due to excessive loosening of their fit and is clearly audible, usually in the form of a double metallic clank when the engine is running at idle speed and warmed up. The simplest way to detect a faulty pin is to alternately disconnect the spark plugs when the engine is running - after disconnecting the faulty cylinder the knocking disappears.

4. Knocking of crankshaft bearings manifests itself in the form of strong metallic impacts, the intensity of which increases with increasing speed.

(Text copied from this resource SKODABOOK.RU)