How to Pinpoint Engine Noise

How to Pinpoint Engine Noise

One of the most challenging tasks you can deal with is diagnosing engine noise. You can use these words to describe noise coming from the engine:

  • Hissing
  • Ticking
  • Popping
  • Knocking
  • Tapping

The sound itself doesn’t tell you where it originates from. Several parts around and in the engine often produce these sounds. For instance, a faulty:

  • Alternator
  • Timing chain
  • Internal engine component
  • Water pump
  • Vacuum line
  • Ignition wire
  • Power steering pump

Different engine parts that usually move at a higher speed, such as pistons, valve train components, accessory pulleys, and crankshafts, can make it challenging to pinpoint engine noise origin.  It would help if you learned how to use simple techniques to find the engine noise source using a few tools and ears.

The procedure in this guide helps you to differentiate between accessories and engine noise. Consequently, if need be, you can use a different method to identify the engine’s internal part, causing the noise.

The following sections outline the most common engine noises that internal components produce when faulty. Remember, this article only highlights the noises that typically rise from the cylinder head and inside the engine block. The guide will not help noises produced by backfires, misfires, or engine accessories such as pulleys, vacuum line, drivetrain, pump, and alternator.

How to Pinpoint Engine Noise

Here’s how to pinpoint engine noise:

  1. Find Out Where the Noise Is Coming From: Is it The Belts and Accessories or The Engine?

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You first need to determine where the noise is coming from before blaming the engine for it. Below are some easy steps to follow:

  • Carefully set the parking brake.
  • Open the hood.
  • Put the transmission to park for automatic vehicles and neutral for manual.
  • Pay attention to the noise after starting the engine.
  • Increase the engine speed gradually and find out whether the noise also increases when you speed up.
  • It’s not an engine noise if the noise doesn’t increase with an increase in speed.
  • If increasing the engine speed causes the noise to increase, then it’s coming from the engine. However, for automatic transmissions, the noise might be coming from the torque converter.

After determining where the engine noise is coming from, eliminate other components like pulleys, accessories, and belts as possible sources. If you are confident the noise isn’t coming from one of the accessories or belts, skip the test and take the next procedure.

Most loose or worn out belts usually produce a squealing sound. If you hear this type of noise:

Use some belt dressing on the belt. If you no longer hear the noise, the belt was the source.

Another way of finding out where the noise comes from is by simply removing the belt you suspect to be the source.

Remove the serpentine or drive belt from your engine.

Use your hand to manually rotate the accessory pulleys where the belts usually run on.

If you find a pulley that feels loose, wobbles or seems unusually hard, that is probably the noise source.

Start the engine, then idle it for a few minutes. Pay close attention to the sound of the engine. Rev up the machine several times. If you can’t hear the noise, one of the accessories or the belt is the noise source.

  1. Does the Noise Come from The Engine Block or Cylinder Head?

Once you ascertain the engine’s noise, you should know whether it originates from the engine block(bottom)or the cylinder head(upper). You can use the strobe light for this procedure. It’s a timing light used on different engine models and comes with a distributor to adjust the ignition timing as part of the tune-up exercise.

Most auto parts stores sell the timing light. Besides, they can also lend you if you don’t own one and are neither looking to buy.

  • Open the car’s hood
  • Use the power clamp to connect the timing light to the car battery. Ensure you follow the right polarity.
  • Use the inductive current clamp to connect the timing lights to the spark plug wires.
  • Ensure the timing light cables are positioned away from engines parts that move
  • Start the car’s engine, then let it idle for a few seconds
  • Direct your timing light to a darker engine surface, then tap the light trigger
  • Please pay close attention to the noise and examine whether it occurs when you flash the lights once or twice

The noise comes from the valve train components if it happens at a flash only. For instance:

  • Camshaft
  • Lifters
  • Rockers Arms
  • Valves

The noise comes from the engine block if it occurs when you flash the lights twice. For instance:

  • Bearings
  • Crankshaft
  • Pistons
  • Connecting Rods

The third section helps you pinpoint the exact component producing the noise using your ears.

  1. Checking for Valve Train/ Cylinder Head Noise

Dealing with cylinder head noises is relatively easy since it’s easily accessible. In most models, the valve train is covered by a metal at the top, and you can easily take it off without removing other significant components. You’ll hear some of these sounds from the cylinder head:

  • Tapping
  • Clatter
  • Puffing noises

You first need to inspect the car. For this procedure, it’s ideal to use the mechanic’s stethoscope. However, you can also use a large screwdriver or a long hose. Be careful with the engine’s moving parts while doing this check as you move the tools around.

  • Start the engine, then carefully set the parking brake and transmission to park or neutral depending on the car type.
  • Open the car’s hood
  • Use the mechanic’s stethoscope or the other tool and move the tip around the cylinder head and the valve cover. Ensure you don’t interfere with other moving components in the engine. If you are using a screwdriver or a hose, press the end on your ears while using the other to detect the noise source around the valve train.
  • Find where the noise is loudest
  • Turn off the car’s engine, then remove the cylinder’s head valve cover that produces the noise
  • After removing the valve cover, start the engine but be careful because the oil will splash out of the cylinder head

Check the valve’s opening and closing to examine if the ones near the noise source are operating differently. Press the rocker arm that sits above the suspected valve and see if the sound stops or changes. If the noise stops, that is the part of the valve assembly with an issue. Check for:

  • Camshaft wear
  • Insufficient lubrication
  • Worn out or damaged rocker arms, lifter, or pushrod
  • Loose valves
  • Contamination, sludge, or dirt around the seal, valve, and spring

  1. Cylinder Head Noises Guide

Try matching the engine sound to the following symptoms as described to zero in on potential components leading to the noise.

Clatter Noise

  • Clatter noise in the valve train is usually caused by:
  • Worn out valve guides
  • Worn out cylinder head components
  • Unadjusted valves
  • Poor lubrication
  • Faulty hydraulic lifters
  • Bent pushrods and valves

First, check that the car is well lubricated, then valve wear and clearance.

  • Tapping Noise

The tapping noise is almost similar to clatter noises. The terms are often interchangeable, but you can hear a distinctive sound when the valves start floating.

A faulty hydraulic lifter, a broken or worn-out valve spring, can cause valve floating. A floating valve cannot close properly, causing the rocker arm to hit the pushrod’s or the valve stem’s top.  It can additionally cause the engine to pop, miss, or backfire.

  • Puffing Noise

Puffing noise from the valve train typically points to a burnt valve. This tends to happen when a part of the valve face breaks due to combustion, causing pressure to escape through the valve. The air-fuel mixture doesn’t burn because the leak gets in the way but causes the cylinder to miss at idle. The puffing noise usually comes from the problem valve, carburetor, tailpipe, or throttle body.

  1. Check for Noise Coming from The Engine Block

It’s difficult to identify an engine block noise than those from the cylinder head as the components are not usually readily accessible. You can pinpoint the source of the noise by doing some practical tests and observing. Noise from the engine block always comes from:

  • Piston wrist pins
  • Piston rings
  • Piston
  • Crankshaft journals
  • Connecting rods

First, you need to identify the cylinder where the noise comes from:

Set the brake at parking, then put the transmission to either Park or Neutral depending on the type of car

  • Check the front wheels and the rear
  • Start the engine, then let it stay idle for a while
  • Move the mechanic’s stethoscope, screwdriver, or hose around the engine block to locate the cylinder with the loudest noise. Always take note of the moving parts when doing the check.
  • Disconnect the spark plug wire on the valve train close to that particular part on the block once you get the loudest point. Check if the sound stops or changes. If you can’t hear any noise, you have located the problem cylinder.

  1. Engine Block Noises Guide

Try identifying similar noises from your car’s engine block using the following engine noise symptoms: Go through the diagnostic descriptions carefully and check if it applies to the noise from your engine. Also, take into account the car’s maintenance history, what you are conversant with about the sound, and any other problems your engine is experiencing at the moment or might have experienced in the past.

Bell-Like Sound

A bell-like sound from the engine block is known as a piston slap or knock. The piston produces a metallic sound as it slaps back and forth on the cylinder wall. Most times, you get to hear this sound when the car’s engine is cold.  As you accelerate, the sound increases in pitch.

What causes the bell-like sound:

  • Damaged piston
  • Worn out cylinder wall
  • Worn out piston skirt

The sound goes away when the engine reaches the standard operating temperature.

Double-Click Sound

You will hear the double-click metallic sound when the engine is idle or at a lower speed.

Here’s what causes the double-click sound:

  • Worn-out bearings
  • Poor lubrication
  • Worn out wrist/piston pin
  • Worn out connecting rod

Rapping Sound

Rapping sound is sharper and metallic rap from the car’s engine block.

What causes the rapping sound:

  • Poor lubrication
  • Worn out bushing or piston pin
  • You can hear the rapping sound when the engine is at standard operating temperature or idle.

A Ticking Sound Especially When Accelerating

Some people describe the engine noise like a high-pitched rattle, chattering, or clicking sound. The pitch tends to increase as you accelerate.

Here’s what causes a ticking sound when accelerating:

  • Worn-out cylinder wall
  • Worn out piston rings
  • Ring lands that are broken

Naturally, a leak-down test will help you know if the piston rings are either loose or broken.

Rod Knock Sound

It’s quite tricky to identify the rod knock sound. The sound always comes from worn out rod bearing that produces a loud metallic knock sound or a light tap. You can hear the sound when the engine is idle or at a higher speed.

Causes of the rod knock sound:

  • Poor lubrication
  • Worn out rod bearing
  • Worn out crankshaft

A quick and dirty way of establishing this problem is to step on the accelerator and release it briefly. You will hear the pitch of the sound increasing.

Engine Knocking Sound

The engine knocking sound is a bit dull but steady and happens when the engine is cold and gets louder when you accelerate.

What causes the engine knocking sound:

  • Worn out crankshaft
  • Worn out main bearings

Conclusion: Using Engine Noises as Diagnostic Tools to Understand the Car’s Engine

Diagnosing noise from the engine is not science. Besides, even professional car technicians find trouble knowing the engine’s problem by only listening to it. However, engine noise is sometimes an excellent diagnostic tool.

The above techniques will help you find the source of the noise and also understand the problem. You shouldn’t ignore the noises and expect them to fade away. Instead, diagnose the noise as soon as you can before it turns into an expensive repair in a flash.

LEARN MORE:

21 Must Have Tools for Mechanics

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