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HOW TO DIAGNOSE THE CAUSE OF NOISE COMING FROM YOUR ENGINE

 

WHAT IS ENGINE NOISE?

Generally, the engine operations always generate noise in the form of sound, but when the sound changed to start generating unusual and unpleasant sound, engineers may refer to it as unusual engine sound called Noise. It is the background or loud blowing sound different from that of the main engine or its previous stable operational sounds.

Unusual noise often develops in engines after using them for a long time, in some cases, it may develop after a short time of heavy loading. The conditions that can cause unusual sounds in engines are enormous but in most cases, the noisy sound may an indication of fault or developing a fault.

According to car engine expert “the malfunction in the engine will reveal itself first as an unusual noise” if it is occurring in a vehicle, the problem may emerge to affect the drivability of the vehicle.

CAUSES OF NOISE IN ENGINES

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Minor deviations from the engine’s initial arrangements such as the loosed pistons, badly worn rings or ring lands, loose piston pins, worm main bearings, and connecting rod bearings, loose vibration damper or flywheel, and worn or lose valve train components, etc. can cause unusual sound in any engine. The combination of one or two of the above deviations can make the sound turn into noise which may lead to other problems in the engine if the signs are ignored. Interpreting or determining the major cause of a noise in an engine cannot be done using a guessing method rather it involves the use of the highly technical method and will require the service of a specialist in the engine diagnosis. However, where there is no availability of a specialist, I will drop little idea on how to go about an emergency situation.

HOW TO DIAGNOSIS ENGINE NOISE

Tracing the source of engine noise can be very frustrating because it may be time-consuming, and may result into other technical issues, therefore it is always advisable to leave it to the expert except you have good knowledge of the engine dismantling and coupling and that the noise has possibility of causing serious damage to the engine parts based on your physical observations.

To proceed, make a noise analyses to be able to remain focused in tracing the source from part to part. To make the analyses and start your diagnoses, use the STETHOSCOPE (a sound listening device) to listen to the engine as it runs. The device will help to amplify the sounds coming from the engine which is a starting point to trace the possible part of the engine the noise is coming from. The device can also help to distinguish between normal and abnormal noise.

HOW TO USE STETHOSCOPE

Place the sound input side into various parts of the engine as it is running to identify the side that the intensity of the noise is high and mark the side and use other criteria to determine the part in that side that could generate such noise. In other words, use the metal prod to trace the sound until it reaches its maximum intensity at that point a better evaluation can be made in regard to the source of the noise.

Another method is to use any electronic sound listening device which can help you to tune the actual sound into the device, thereby canceling other sounds from the engine and helping to trace the side with the maximum intensity quickly.

Macro Focus Cogwheel Gear Engine Vintage F

TYPES OF ENGINE NOISES

The entire sound of an engine is a product of the various noises coming from the actions of the moving parts but the unusual sound which is termed as a noise means a deviation from the already existing sound.

Any engine can develop noise and the following parts of the engine are known to be the frequent source of engine noises:

PISTON RING NOISE

The unusual sound of the piston ring can be heard during acceleration as a high-pitched rattling or clicking into the upper part of the cylinder. It can be caused by worn rings or cylinders, broken piston ring lands, or insufficient ring tension against the cylinder walls. The problem of the piston ring noise can be solved by simply replacing the rings, pistons or sleeves or re-boring the cylinders.

PISTON SLAP NOISE

The noise is usually heard when the engine is cold and often gets louder when the vehicle accelerates. It occurs when the piston slaps against the cylinder wall, resulting in a hollow, bell-like sound. The cause of the slap may be as a result of worn pistons or cylinder, misaligned connecting rods, collapsed piston skirts, excessive piston-to-cylinder wall clearance or lack of lubrication which may lead to worn bearings.

To solve the issue of piston slap, the following may be required; replacing the pistons, re-boring the cylinder, replacing or re-aligning the rods, replacing the bearings, and removing the spark plug of the affected cylinder.

PISTON PIN KNOCK NOISE

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The noise is a sharp, metallic rap that can sound more like a rattle if all the pins are loose. It originates in the upper portion of the engine and is most noticeable when the engine is idling and it’s hot. It sounds like a double knock at speeds.

The causes of such noise are; worn piston pin, piston pin boss, piston pin bushing, or lack of lubrication, resulting in worn bearings. The problem can be solved by either installing oversized pins or replacing the boss or bushings or replace the piston.

RIDGE NOISE

It is a very common and distinct noise as it occurs as the piston ring strikes the ridge at the top of the cylinder, the result is a high-pitched rapping or clicking noise that becomes louder during deceleration.

Though may factor can contribute to this, but one known factor is when new rings are installed without removing the old ridge, the new rings will contact the ridge and make a noise. Another factor is when the piston pin is very loose or the connecting rod has a loose or burn-out bearing, the piston will go higher and strike the ridge at the top of the cylinder making a high-pitched rapping or clicking sound.

To correct the ridge noise, remove the old ring ridge and replace the piston pin or piston.

ROD-BEARING NOISE

This is a noise arising as a result of worn or loose connecting rod bearings, this noise is heard at idle as well as at speeds over 35 mph depending on how badly the bearings are worn, the noise can from a light tap to a heavy knock or pound. Shorting out the spark plug of the affected cylinder can lessen the noise unless the bearing is extremely worn. The noise is usually caused by a worn bearing or crankpin, a misaligned rod, or lack of lubrication, resulting in worn bearings. The problem can be solved by servicing or replacing the crankshaft, realign or replace the connecting rods and bearings.

MAIN OR THRUST BEARING NOISE

It is a noise from the loosed crankshaft main bearing which produces a dull, steady knock, while the loose crankshaft thrust bearing produces a heavy thump at irregular intervals. The thrust bearing noise might only be audible on very hard acceleration. Both of these bearing noises are usually caused by worn bearings or crankshaft journals. To correct the problem, replace the bearings or crankshaft.

TAPPET NOISE

It is a light, regular clicking sound that is more noticeable when the engine is idling. It is caused by excessive clearance in the valve train. Another cause may be improper valve adjustment, worn or damaged parts, dirty hydraulic lifters, or lack of lubrication. The problem can be solved by adjusting the valves, replacing any worn or damaged parts, or clean or replace the lifters.

ABNORMAL COMBUSTION NOISES

They are the pre-ignition and detonation noises caused by the abnormal engine combustion.

Detonation knock is or ping is a noticeable noise during acceleration mostly when the engine is under load and running at normal temperature, and its excess can harm the engine. The frequent cause of detonation is advanced ignition timing or substantial carbon deposits that get so hot, glow and re-ignite the air/fuel mixture in the combustion chamber causing a usual combustion as detonation. Another cause may be a fuel with octane that is too low.

The problem may be solved by removing carbon deposits from the combustion chambers with a rotary wire brush and using higher octane gasoline. Another possible cause can be a malfunctioning EGR valve.

 

 

Originally posted 2018-07-15 05:24:51.

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