6 Causes Of Knocking Sound From The Engine

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Have you ever wondered what is engine knocking and what causes your engine to knock? Well, knocking occurs when fuel burns inconsistently in your engine. When everything goes smoothly, and the cylinders have a correct mixture of air and fuel, the fusion burns in an intensifying manner.

But how do we know if our engine has been knocked? So, the answer to this question is, “If a repetitive striking or tapping sound is coming from your engine very loudly when you accelerate, then it is a sign that your engine has been knocked.”

Apart from this, there are numerous different types of noises described by knocking in engine that are caused due to certain individual issues, and searching the source for the engine knock noise is one of the trickiest parts as we are not able to figure out what is the possible cause of engine noise.

But in order to make it easy for you, we have come up with some most common causes of knocking in engine. Let’s dive right into this blog in order to understand all that you need to know regarding this problem. But before jumping into the causes let’s first understand what is Engine Knocking.

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What is Engine Knocking?

When a weird knocking sound from engine is produced or your engine produces striking and tapping noises, then it is known as knocking in engine. In short, when there is knocking of petrol in your car or engine, then it is called ‘knocking in engine.’ When you accelerate hard and the fuel inside the engine burns inconsistently, then it forces the noises to become louder. 

The inconsistent burning of fuel is the main reason that causes different patches of combustion. This develops several flame fronts inside the engine. Whenever a patch is burnt, a slight shock is generated which burns other patches and this always keeps the process ongoing

Engine Knocking

The cylinder pressure boosts remarkably due to the shock wave, which produces a different metallic striking sound. The knocking engine can have subsidiary to totally noxious or destructive effects. You must not get confused between what is engine knocking and pre-ignition as these two are different phenomena but pre-ignition can be followed by knocking.

Why Do Engines Overheats? 

If you have understood what is engine knocking or what is knock in engine, then there will be no problem in understanding why does engine overheats and why knocking of petrol occurs.

Well, there are many reasons why engines overheat but normally it is because there can be some issue in the cooling system and the heat was not able to get away from the engine compartment. These sources of problem can include a faulty radiator fan, clogged coolant hose, cooling system leak, or broken water pump.

Why Do Engines Overheats?

Nevertheless, the issue’s source, an engine that has overheated is not something that you want to remain stay. It can be a serious problem and threat to your engine if not seriously dealt with it.

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What Are The Signs That Your Engine is Overheating 

If you are able to figure out what is knock in engine, then you will be able to take action to cool your engine before it gets overheated, and you will be able to reduce the risk of irreparable engine damage or engine knocking.

But first of all, let’s discuss the signs of your engine overheating which will help you to learn what is knocking in engine.

- Steam: It looks like smoke and it comes from under the hood of the car.

- An engine temperature gauge on your dashboard that has a symbol of ‘H’ or has a red mark. Make sure that engine temperature gauge symbols differ from each other, as a result, you must consult your owner’s manual.

- A weird smell comes from the engine area. For instance, leaking oil will smell more burnt whereas leaking coolant can smell sweet.

What Are The Causes of Engine Knocking? 

Engines have several moving parts and when you begin to hear knocking, tapping, or out-of-the-ordinary sounds, then it can be a serious problem. Here we have mentioned a few reasons why you might be hearing a knocking sound. Along with these, we have come up with certain reasons that cause the engine to knock and what is knocking in engine.

Causes of Engine Knocking

Primarily, we should know what detonation knock is, i.e. when your engine is working swiftly and running smoothly, then the fuel/ air mixture burns up by oneself and control the detonation inside each cylinder.

The knocking or rattling noise that you will hear when the fuel and air mixture in the cylinders is detonating in more than one spot at a time is known as a detonation knock. The parts of the fuel/ air mixture will start to ignite very quickly and early and when these small fireballs will collide, then it will create a knocking noise.

You are able to experience what is knocking of engine when you place fuel with a cheap octane rating but you cannot feel the engine knock if your car has a performance-regulated engine that is rated for high-octane fuels as these high-octane fuels are able to burn more identically and hence it resists knocks.

As a result, if you place systematically lead-free in your car that will demand top-quality fuel, and this can be the source knocking sound in your car. Make sure to check the owner’s manual in order to find out which octane rating is fine for your car.

The possible source of engine knocking is not always coming from the engine itself, but it could be also from the accessory belt. When the engine runs, it turns the belt that is connected to several pulleys all around the engine bay.

This belt must be an accurate amount of tension so that it can be turned quietly and smoothly. If the belt becomes extended, one of the pulleys is bent out of shape, or the tensioner is not working properly, still you can hear tapping, striking, rattling noises that can be mistaken for engine knock.

But fixing a noisy accessory belt is as simple as replacing the belt, adjusting the tension, or replacing the bad tensioner or accessory pulley.

3. Rod Knock: Worn Bearings

The next type of engine knocking is rod knock. When the pistons travel up and down in the engine, they rotate the crankshaft which eventually releases power to the wheels. These rod bearings enable smooth pistol movements, but they are able to come out or wear out of position over time.

When these bearings are worn out, the pistols will start to clunk against the crankshaft which will create much of a muchness sound.

In order to fix this issue, you will need new bearings or other work done on the crankshaft or pistons. These are those parts that are located deep inside the engine.

Fortunately, an explosion or an engine knock is not an often issue with modern cars, since the fuel/ air ratio, fuel timing, and injectors are all controlled by computers. There is also a knock sensor that has been designed in order to detect engine knocks and inform the Engine Control Unit so that it can rectify the problem systematically.

As a matter of course this means that a substandard knock sensor is able to allow the engine to knock. 

Issues with the fuel injectors, oxygen sensors, mass airflow, or fuel pump sensors are able to build a slant fuel/ air mixture inside the engine. This slant fuel/ air mixture doesn’t have sufficient fuel and extravagant air.

Without enough fuel in each cylinder, the mixture will not be able to burn faster, and this will allow for several detonations which will cause the engine to knock. 

The majority of modern cars have the timing of the engine i.e. at which time and point the spark plugs in the engine will catch fire and is controlled by the computer. But if for any matter the spark is not catching fire when it should, then it can cause several detonations in the cylinder, which will undoubtedly result in an engine knock. 

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What To Do When Your Engine Overheats? 

You must turn off the air conditioner instantly and without any further delay in order to reduce stress on the engine. After that, turn the dial to the utmost heat. Doing this will help you to pull heat away from your engine and you will be able to keep it away from overheating until you can draw up to a safe location

After you have completed your first step of terminating the A/C and increasing the heat, then you must search for a safe place and stop your car straight away. Then make sure to make your engine cool for not more than 20 minutes in an open area or a field. You must keep your one eye on the temperature gauge, as it should back away to an ordinary range as the engine cools down. 

If you have a limited coolant level, then a quick top-off can help you to protect your engine and prevent overheating until you can get things secured and fixed. Nevertheless, this step is not able to do something amazing if a coolant hose is blocked or obstructed or the source of the trouble is a ruptured radiator fan or water pump.

You must confer and negotiate your owner’s manual in order to find out the location of the coolant reservoir tank and to understand how to add coolant to your vehicle.

4. Restart The Engine

If your vehicle has not been towed, then it’s time to meticulously restart your engine and drive to your nearby repair shop. You must keep one eye on the temperature gauge when you will be driving. If the heat rises again, then you must pull over again and stop the engine and let the system cool down.

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What Not To Do When Your Engine Overheats?

You must keep yourself cool in this situation when it's knocking in the engine. Make sure to avoid deviating from traffic or banging your brakes when you will be pulling off the road.

You must stop driving if your engine is overheating or knocking noise is produced by the engine otherwise it can cause consequential and costly damage to your vehicle if you will be pushing your engine too far.

Once you pulled over and you stopped the car, you must wait for the engine to cool down before opening the car’s hood in order to check it out. If you will open the hood immediately when the engine is overheated or knocked and steam is coming out of the engine, then it may cause you burn injuries from that spewing smoke or steam.

You must wait until the engine is cooled down and the temperature of the gauge has been settled before opening the car’s hood. 

The problem of an overheated engine will only get worsened if you will leave it unexamined. As a result, it has been advised to you that you must ensure and understand the reason behind this trickiest problem in order to fix your engine’s issue. 

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Conclusion 

Now you would have understood what is knocking of engine, what is knocking sound from engine, what are possible causes of engine noise, and how to prevent your engine to knock. Routine examinations will help you to fix any possible radiator or engine problems before they get worsened.

It will also help to reduce engine knocking. The perfect way to put a stop to the knocking car engine is to put frequent and regular coolant flushes, and you must keep up with its maintenance on a regular basis as suggested by your car manufacturer. 

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By: Varsha Ojha

Wed, Nov 08, 2023

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