Causes of Piston Noises

Causes of Piston Noises Points : causes of piston noises, engine noise analysis, problems in internal combustion engines, ic, engine, auto diesel The most common piston noise is a slap due to the rocking of the piston from side to side in the cylinder. Although income engines piston slap causes a clicking noise, usually it causes a hollow, muffled, bell-like sound. Slight piston noises that occur when the engine is cold and disappear after the engine is warm do not ordinarily warrant correction. Piston ring noises generally cause a click, a snap, or a sharp rattle on acceleration.

Short-circuit the spark plugs to locate piston and ring noises. As this test will affect other engine noises, sometimes the result is confusing. To detect piston slap more accurately, drive the engine at low speeds under a load. The noise generally increases in intensity as the throttle is opened and additional load is applied. On some engines with very loose pistons, a piston rattle is encountered at speeds between 30 and 50 mph when the engine is not being accelerated.

To eliminate piston and ring noise momentarily, put 1 to 2 oz. (ounces) of very heavy engine oil into each cylinder through the spark plug hole, crank the engine for several revolutions with the ignition, turned off, until the oil has worked down past the piston rings. Then install the spark plugs, start the engine, and determine.

Whether the noise still exist. If not, the noise probably is due to one of the following causes:
1. Collapsed piston skirt
2. Excessive piston-to-cylinder bore clearance
3. Eccentric or tapered cylinders
4. Piston pin too tight
5. Connecting rod misalignment
6. Piston or rings hitting ridge at top of cylinder bore
7. Piston striking carbon accumulation at top of bore
8. Piston interfering with cylinder head gasket
9. Broken piston rings
10. Excessive side clearance of ring in ring groove
11. Piston pin hole out of square with piston
12. Ring lands not properly relieved