Started the car and heard an obscure flump from the hood? What's happened? Where to look for a problem? The reasons may be different. In this epitome, we will comprehend the reasons for knocking in the engine, how to distinguish and eliminate it faster than the breakdowns turn stronger.


What is engine knocking?

What does it mean when your engine knocks? How to know if the engine is knocking? Why does it happen and what noise points out the issue?


Knocking in the motor is a normal process, pointing out the operation of the system. With proper operation, air and fuel enter the cylinders evenly, gasoline/diesel burns in a controlled manner. After that, the mixture creates a small bump inside. This is the sound that you hear during normal operation of the motor, and it’s ok. But the clatter may also indicate some malfunctions of the vehicle. Anyway, listen to the car and try to define if the clatter is similar to the following noise. 


Symptoms of engine knock

You’ve already known that there is a normal sound, and there is an unnatural one. And if you hear some atypical sounds for your car, try to understand the issue. Let's analyze the main engine knocking symptoms:


  • a motor clunk which gets louder as you hit the gas;

  • dynamic clatter;

  • loud thud at the top of the motor;

  • constant ringing noise at the top of the node;

  • disappearing noise at idling and up turnovers;

  • a expressive metallic clatter that intensifies with a sharp opening of the throttle valve;

  • the sound is like undercutting elements of the exhaust system.


To determine how dangerous an atypical sound is, we recommend doing three things:


  • define the nature of the sound: temporary or constant;

  • find out the tonality — ringing or subtle;

  • open the hood and try to spot where the sound is coming from, then it will be easier for you to make a causal relationship and communicate with a specialist (at the service station, the master uses a special stethoscope, which directs to various areas to find the source of the sound).


The motor is the most important element of the car, therefore, at the first unusual clatter, we recommend you to go to the station and contact the specialists. If you don’t know the peculiarities of the automobile and have never encountered this before, then trust the professionals and let them check the car. 

What causes engine knocking

What causes a knock in an engine? A question that worries every motorist after a symptom is detected. The reasons can be both simple and really serious, which lead to a complete replacement of the node. However, we won’t scare you, but let's talk about the most prevalent reasons:

  • low oil level or its low quality;

  • defective spark plugs;

  • low octane gasoline;

  • carbon deposits in the cylinder;

  • worn bearings;

  • unlubricated cylinder upper part;

  • faulty fuel pump;

  • worn gaskets or spigots. 


If you can determine the low level of oily fluid and enlarge the octane number in the fuel yourself, then it is difficult to define other causes without the help of a specialist. Let's deal with each item in more detail. 

Low oil level

When the oil level is low in the motor, the parts don’t receive enough lubricant. Therefore, they can click and make obvious friction sounds. It is quite simple to be persuaded that the clanking noise in engine appeared precisely because of the lack of oil fluid. Check the dipstick, which you can see under the hood, next to the head of the block. The handle of the rod is often painted in a bright color to make it easier to replace. If the oil on it is below the mark, then it must be topped up, if it is too dark, replace it.


We recommend using Bizol oils, which are developed using certified materials and German engineering experience. The company manufactures oils for passenger cars both on gasoline and diesel fuels. The Green Oil + range is designed for hybrid vehicles and start-stop systems that are used in urban traffic.

Defective spark plugs

Spark plugs help in starting the motor. They supply an electrical scintilla, from which the air-fuel mixture of the cylinder is ignited. Spark plugs, like any parts of mechanisms, stale, break and become clogged. Their malfunction leads to a decrease in motor power, which causes a knocking sound in engine. The only solution to the problem is to change the spark plugs.

Low octane gasoline

Fuel differs from each other, foremost, by the degree of octane number. The higher it is, the cleaner the gasoline and the greater the compression ratio it can withstand. There are motors that are designed to work only with high-octane fuel. If you constantly fill them with gasoline at a low rate, you will catch the engine is making a knocking noise which isn’t like the usual one. Therefore, we recommend you adhere to the manufacturer's standards and use the right fuel.


Special fuel additives can also be used to increase the octane number. We recommend BIZOL GDI POWER CLEAN. This is a fuel additive for restoring the performance of a gasoline direct injection engine: GDI, CGI, TFSI, TBI.


Clean injectors are crucial for the correct operation of the assembly. Contaminated ones will not be able to provide the required amount of fuel. The additive contains a detergent based on polyesteramines. It removes deposits and prevents their formation, which leads to the restoration of motor performance. Significantly reduces the effect of LSPI.


GDI Power Clean
GDI Power Clean 0.5L
GDI Power Clean 0.5L
GDI Power Clean
  • Effectively removes deposits on the surface of the injector needle tip and throughout the combustion chamber   

  • restores the original performance of the engine  

  • ensures regular engine running and reduces fuel consumption  

  • reduces maintenance costs  

  • ensures environmentally friendly, low-pollution combustion  

  • reduces the risk of engine damage due to LSPI (Low Speed Pre-Ignition).

          Carbon deposits in the cylinder 

          When fuel is burned, carbon deposits can set in the cylinder. Their presence reduces the space for air and gasoline, causing an enlargement in compression. Therefore, you can hear knocking in motor. It is possible to identify and eliminate carbon deposits only with the help of a specialist.

          Worn bearings

          Over time, the bearings between the crankshaft and the cylinders wear out and can create excessive noise. Also, the reason for this may be excessive dirt or soot that forms on the back of the part. Worn bearings can damage the haulage, causing it to slap or rattle in the car. Replacing the node will help to prevent this problem.

          Insufficiently lubricated cylinder upper part

          An unlubricated cylinder head can damage the piston rings and cylinder walls that prevent piston strikes. A sufficient amount of oil is needed for smooth operation of the cylinders. If the part is not sufficiently lubricated, a loud engine knocking will be heard. Most often this happens due to leakage of engine oil, at its low level.

          Faulty fuel pump

          The fuel pump is responsible for supplying fuel to the system. When it is absorbed, the liquid may not fall into the required amount and the pressure will be lower. Which caused the extra noise. Also knocking can be if the air-fuel admixture becomes richer.


          In any case, only a mechanic can solve this problem. He will determine whether the pump can be repaired or if a complete replacement is required.

          Worn gaskets or spigots

          Special gaskets or seals are installed between many parts in the motor that reduces the impact force of the mechanisms and decreases noise. If you hear a sound that resembles ringing blows on metal, then most likely the gaskets are worn somewhere. You can fix this by simply replacing them with new ones.


          Can you drive a car with a knocking engine?

          Definitely not! Even small problems that make a clatter in the motor can cause serious damage. Replacing the main parts of the motor or even the motor itself can cost you a lot. Therefore, if you hear a knocking noise in engine, go to the service station, mechanics will tell you how to fix it and why it arose.

          How to prevent knocking in engine

          To prevent the appearance of unwanted clatter in the car, follow the basic rules:

          1. Get a technical inspection once a year.

          2. Use gasoline with a certain octane rating.

          3. Change the oil on time and monitor its level.


          As you hear a noise from the engine that borders metal tapping or clanging, it is better to contact a specialist in order to know how to fix an engine knock.  Forehanded repair of breakdowns will save you money. After all, a complete refit of the node will take your time and adjust the monthly budget.

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