Engine rattling, buzzing, or knocking: What is the problem?

Published at

There are malfunctions that even an experienced motorist cannot detect without equipment. However, such malfunctions can also be detected in time without any equipment.

You will simply need only your senses, or more precisely, one which is your hearing.



Some malfunctions can be spotted easily without much trouble. Drivers who know their car very well, know how it behaves, and thus can notice sooner when something is wrong with the car also have an advantage. However, if you know which component announces its failure with a specific sound, you won't get lost even when buying a second-hand car.

Listening to various sounds from the car has its advantages. If you are able to recognize them, you might be able to detect an innumerable number of malfunctions and problems, which are often still in their infancy. It is, therefore, possible to detect these faults before they could negatively affect the car's driving, consumption, performance, and other parameters or damage other parts and components.

Since the car is made up of countless components that can indicate their failure with different sounds, we decided to prepare a series of four articles on this topic. In these articles, we will focus on a certain part of the car and its components, which can indicate their malfunction with different sounds.

In today's article, we will look at the most important part of the car, namely its engine, and drivetrain.

Can you recognize the malfunction of the engine or drivetrain by its typical sound?

Sound: Heavy, metallic knock

Possible cause - Worn crankshaft bearings.

Solution - Replacement of the bearings.

Sound: Rattling when the clutch pedal is depressed

Possible cause - Failing clutch thrust bearing.

Solution - Replacement of the bearing if this problem is detected and confirmed.

Sound: Ringing clutch at idle

Possible cause - Cracked clutch plate springs.

Solution - Replacement of the damaged part or the whole clutch.

Sound: Knocking at idle

Possible cause - Worn dual mass flywheel.

Solution - If the knocking sound is heard only when the engine is cold, the replacement of the flywheel is not urgent, or it does not need to be replaced immediately. However, if the dual-mass flywheel exhibits such acoustic problems permanently under any conditions, its replacement is necessary.

Sound: Rattling sound from the transmission at idle

Possible cause - Backlash in the gears of the gearbox.

Solution - These sounds are related to the tolerance of individual parts and are, in most cases, harmless.

Sound: Humming from the gearbox while driving

Possible cause - Worn bearings in the transmission or transfer case.

Solution - Replacement of the worn parts.

Sound: Metallic rattling from the engine shortly after starting

Possible cause - Hydraulic tappets (hydraulic valve lifters) with insufficient oil pressure.

Solution - Not necessary if this sound disappears a few seconds after starting. However, if the metallic rattling persists for a long time, some of the hydraulic tappet is probably damaged, which means that it needs to be replaced.

Sound: Buzzing noises when the engine load changes (acceleration/deceleration):

Possible causes - Loose or worn motor mount.

Solution - It is necessary to tighten or replace the damaged motor mount.

Sound: Rattling noises from the engine

Possible causes - Timing chain slack or bad timing chain tensioner.

Solution - Replacement of the entire timing set or just the timing chain tensioner.

Sound: Buzzing or hissing after turning on the engine

Possible cause - Fuel pump working sound or fuel pump wear.

Solution - If this acoustic signal of the fuel pump is heard only a few seconds after turning on the engine, it is normal. However, if this noise is loud and the fuel pump is heard constantly, adversely affecting the engine, it is almost certain that the fuel pump is at the end of its lifespan.


Of course, there are countless other malfunctions of the engine and its components, manifested by similar acoustic or other manifestations. However, these are some of the most common problems detectable by hearing.

In the following article, we will shed light on several faults in chassis and brake components, which can also be detected without equipment, just by hearing.