Can faults be identified by engine noise?

The presence of noise in the engine is a sign that something is not working correctly. Identifying the source of the noise and its cause may provide a clue, but not the complete information needed to troubleshoot the problem. Let's look at some of the common types of noise you may find in your engine.

Sounds synchronized with engine rotation

The intensity of the noise that occurs during engine operation may vary depending on engine speed. There are various types of noise in this category:

• Metal bumps or knock. This is a metallic noise that occurs in the combustion chamber. One of the reasons may be poor quality fuel, a mixture of air and fuel with an excess of oxygen or a distributor in poor condition.
• Crashing valve springs. The valve springs produce a rattle sound when they are loose or in poor condition.
• Noise in piston rings. Reminds a dull metal noise. Occurs when these rings or segments are broken or worn. One of the consequences is increased oil consumption.
• The noise of a “sewing machine”. It is named so for the similarity of the sound with those produced by these machines. The reason why this noise occurs is usually the slack between the stop and the tail of the valves.
• Whistle. As a rule, the whistle in the engine comes from the cylinder block. As a rule, valve seats are in poor condition or there are cracks in the head gasket. Usually this whistle is rhythmic, synchronized with the engine.

Noise in the cylinder head at each engine revolution

These sounds can warn of a malfunction in the cylinder head, pistons or valves, and the sound intensity, as a rule, does not change with increasing engine speed. Typically, such noises are a sign of a potentially serious malfunction, and therefore, as soon as such sounds appear, it is advisable to stop the engine and check it. Two types of such noise can be distinguished:

• Thud. A dull and deep noise may indicate that a piston is faulty. Poor lubrication is one of the most common causes of damage to internal vehicle components.
• Metal knock. Typically, the result is the contact of a piston with a valve. If the blow is dry and metallic, which may indicate serious engine damage. Being broken, the piston may bend or break the valve.

Other typical engine noises

• Echo. It occurs during acceleration, and is heard like small explosions. It is usually caused by defects in the joints of the exhaust.
• Rattle noise. This is one of the most common noises and occurs when one part rubs against other metal parts. May be caused by parts that were not properly secured, such as a generator or fan. In addition, if the engine is overheated, it is likely that the problem lies in the poor condition of the bearings of the water pump.
• Turn rattle noise. When this noise is heard only in corners, it means that the oil level in the crankcase is insufficient. When turning, the engine runs almost dry, hence this noise.
• Residual noise. This is the noise that occurs when the ignition key has already been removed. This sound subsides, is triggered by a piston, and continues for a short period of time. The sound is not like metal. May be caused due to excessive soot, poor engine idle adjustment, or because the engine is operating at too high a temperature.

These noises are only an indicator of where the problem might be. It is the responsibility of the professional to inspect the entire engine thoroughly before confirming the malfunction.

Questions and answers:

What is engine diagnostics? This is a test of the operability of all sensors and electronic systems of the power unit. The operation of all units and systems responsible for the operation of the motor in different modes is being tested.

How to diagnose an engine? The air filter, spark plugs, armored wires, timing chain or belt are checked, the compression in the cylinders is measured, errors are eliminated using diagnostic equipment.

What are the outward signs of an engine malfunction? Extraneous noise during operation, strong vibrations, oil drips, color of smoke from the exhaust pipe. All these parameters allow you to identify some motor malfunctions.