Car Knocking Sound After Turning Engine Off - Causes And Solutions - Car Super Care (2023)

Quick Navigation

  • What Causes The Knocking Sound?
    • Exhaust System Contracting
    • Cold Weather
    • Loose Engine Mount Or Driveshaft
    • Cooling Fan Off Balance
    • Reduced Oil Pressure
    • Sensors
    • Using The Wrong Spark Plugs
    • Pulleys And Belt Tensioners
    • Damaged Head Gasket
    • Coolant Tanks
  • Solutions To the Car Knocking Sounds
    • Always Check The Sensors
    • Replacing Your Rod Bearings
    • Regular Servicing Of Your Vehicle
    • Replace The Spark Plugs
    • Fuel Detergent
    • Changing The Oil And Filter
  • Final Verdict

Is everything okay? I know that is the first question you will have once you hear a knocking after turning the engine off.

Having your car checked anytime, you have doubts or there are weird noises will save you money and disappointments in the future.

Although the car knocking sound after turning off the engine is not always an indication of a problem, being sure doesn’t hurt.

Car Knocking Sound After Turning Engine Off - Causes And Solutions - Car Super Care (1)

Every car owner understands how delicate and expensive a car’s engine is. I’m sure you do not want to be in a position where you must change your engine.

Tackling the engine problems head-on will help avoid any future losses or problems.

Below are some causes and solutions to a car knocking sound after turning off the engine.

What Causes The Knocking Sound?

Let’s dive in and look at all the possible causes of the knocking sound.

Exhaust System Contracting

After a long drive, while using a turbo-powered car, you might hear a knocking sound after turning off the engine.

It is a result of the contraction of the exhaust system. The sound is typical, and you don’t have to worry about it.

You can always avoid it by letting the car run for a minute after a long drive off. You can also consider using a high fuel octane rating.

Cold Weather

It is highly likely to experience a car knocking sound after turning off the engine on freezing days or in the winter.

(Video) The Engine Sound You Never Want to Hear

After the car is turned on, heat is generated, and once it’s shut off, the metal parts contract due to the cold; hence, the knocking sounds after turning off the engine.

Loose Engine Mount Or Driveshaft

Loose engine mounts could also result in a knocking sound after turning off the engine.

When the driveshafts or engine mounts get loose, the engine also becomes loose and starts moving around, hence the knocking sounds.

The only solution to this problem is having these mounts checked and fixed before more trouble escalates.

Cooling Fan Off Balance

You might also experience car knocking sounds after turning off the engine if the cooling fan is not in the correct position.

The fan could be hitting something and hence the knocking sound. Let someone else turn the car off after the fan has been running and check how it’s positioned.

Reduced Oil Pressure

During shut-off, oil pressure reduces due to the sudden stop. In most cases, the knocking sounds occur in the last spins before the car shuts down completely.

It takes less than a second.

Sensors

Most vehicles are now computer-controlled and have sensors that can detect every problem in the car. The sensors will alert you every time there is a problem.

A signal is first sent to the engine control unit to fix the problem.

Sometimes even after the problem is corrected, the sensors will still alert you; if you are shutting off your car, you will probably hear the knocking sound after the engine is turned off.

Using The Wrong Spark Plugs

The wrong spark plugs may fail to ignite all the fuel causing a knocking sound after turning off the engine. You can quickly identify bad spark plugs.

Sometimes the spark plugs may be worn out and require a switch, or you are simply using the wrong type of spark plugs in your vehicle.

Pulleys And Belt Tensioners

The knocking sounds after turning off the engine might seem like they are coming from the engine, while it’s not the case.

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There is a variety of moving equipment down there, and as the car moves, they might collide, causing a knocking sound.

After the engine is turned off, the engine accessories and all other equipment do not halt abruptly.

On the contrary, they turn a few more times, causing the knocking sound. Another major cause of the knocking sound after turning off the engine is a faulty lifter.

The sounds could be alarming or not, depending on the magnitude of the destruction.

If the knocking sound is too much or proceeds for a long time, it could indicate too much destruction.

However, if the knocking sound is brief, it may result from accumulated dirt and dust.

Car Knocking Sound After Turning Engine Off - Causes And Solutions - Car Super Care (2)

Damaged Head Gasket

A damaged oil gasket will cause knocking sounds when driving and after turning the engine off.

The reason is that it exposes the coolant system to external materials like dust particles.

Coolant Tanks

Another cause of the knocking sounds after turning off the engine is the coolant tanks.

Some vehicles come with coolant tanks that create some noises after the engine is turned off. In most instances, the noise is no problem at all.

Solutions To the Car Knocking Sounds

Having learned the different causes of the engine knocking sounds, you must identify ways to solve the problems.

Most of the time, the sounds are not alarming, and you only need a check-up to get everything cleared out.

Always Check The Sensors

A bad knock sensor will misinform you. Therefore, ensuring your sensors are okay and working will help avoid any problems in your car or misguided information.

(Video) How to Easily Diagnose and Fix Engine Knock

Replacing Your Rod Bearings

Whether you use your car regularly or once in a while, you need to get the bearings checked.

Some people can tell when the bearings require changing, and some will get an idea after an engine knock.

Having the engine and all accessories changed after continued use can solve the problem of a knocking engine.

Regular Servicing Of Your Vehicle

As we have seen earlier, the knocking sound is probably not coming from the engine.

If your vehicle is serviced regularly, your mechanics can realize what needs to be changed or what could bring about any weird sounds or other problems.

Replace The Spark Plugs

Different spark plugs are made for different temperatures. The wrong spark plug will experience heat intolerance hence a spark knock.

Carbon build-up usually coats the electrodes and narrows the gap resulting in the knock.

It would help if you used the correct spark plugs for your vehicle and maintained the proper gap.

Fuel Detergent

Fuel detergents help a great deal in preventing engine knocks.

The detergent fuels help reduce carbon accumulation in the cylinder walls and on the spark plug electrodes.

The accumulated carbon causes premature fuel-air detonation and, after that, a knocking sound.

Therefore, getting file detergent and more suitable fuel detergent will prevent engine knocks after the engine is off.

Changing The Oil And Filter

Oil is an essential aspect of every engine. Some engine problems emanate from substandard oil or failure to oil the different parts.

Engine knocks can occur when different parts collide, especially if not oiled.

(Video) How to Fix Rattling Engine Noise in Your Car

Lubricating the different engine parts helps distribute oil and remove metal filings and other dirt particles.

Also, using good-quality lubricating oil will help a great deal in avoiding engine knocks.

Final Verdict

You never know what to feel about an engine knock. Sometimes, it may be a warning of a roaming problem, while in some instances, it is a non-issue.

In most cases, only mechanics and trained personnel can identify whether a particular engine knock indicated a red flag or not.

While it’s not always a cause for alarm, you should always have it checked after experiencing knocking sounds after turning off the engine.

Car Knocking Sound After Turning Engine Off - Causes And Solutions - Car Super Care (3)

James has been a car enthusiast since his childhood when he learned the differences between a ford and a chevy from his father. He loves to drive and restore old cars with a special drive for Italian marvels. Currently, he has a 1968 Alfa Romeo. He has studied aeronautics and civil aviation in his college and still gets smitten by Galant SS and Lancer GSR.

He is a New York-based product training director working with a giant automotive retailer. He loves to review and uncover the vehicles and their fascinating stories. He believes in keeping it legitimate with a keen passion for research on the latest technological upgrades in cars. While reading his articles or blogs, you can sense the extensive research and dedication backing the piece of text. He loves fried chicken, music, and spending quality time with his pet dog.

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FAQs

Why does my car make a sound after I turn off the engine? ›

If your car makes a metallic clicking sound after you switch off the engine, it's just the sound of the engine cooling down. It's nothing to worry about and will stop of its own accord fairly quickly.

How do you get rid of engine knocking noise? ›

How to Fix Engine Knocking
  1. The first step in trying to fix engine knocking is to upgrade to gasoline with a higher octane rating. ...
  2. Give your engine a tune-up that includes new spark plugs and wires.
  3. Regularly change the oil in your vehicle and monitor for a low oil level.
Mar 20, 2020

What is the main cause of engine knocking? ›

Commonly, engine knocking occurs because of a buildup of oily carbon deposits inside the combustion chamber. This can be caused by burning oil or incomplete combustion from misfires, which coats pistons, cylinder heads, and other parts of your engine with residue.

How much does it cost to fix a knocking engine? ›

A knocking sound coming from your car's engine can indicate an issue with the crankshaft journal and bearing, which are hitting each other. It's not exactly a simple fix, so auto shops tend to charge anywhere from $2,000 to $3,000. Some repairs can run up to $4,000 if the damage is severe.

What is the popping sound after engine is turned off? ›

More than likely the noise is caused by the exhaust system cooling down. It can make a crackling sound as the metal contracts as it cools. It's perfectly normal for this condition to occur. It is the engine cooling off.

Why does my car make a weird noise when stopped? ›

If your car makes rattling noises when stopped in drive it could be due to loose parts, an item stored in your car or a more serious problem that's cause for concern including: Failing catalytic converter. Loose heat shield. Low oil pressure.

Can a knocking engine be saved? ›

How Do You Fix Rod Knock? The only solution is an engine rebuild where you pull the rods and replace the bearings. It's likely that the flailing rod damaged the crank journal surface, so you'll definitely need the crank polished and most like turned.

What is the gas additive for engine knocking? ›

Ferrocene and its derivatives are antiknock agents added to the petrol used in motor vehicles, and are safer than the now-banned tetraethyllead. Petrol additive solutions containing ferrocene can be added to unleaded petrol to enable its use in vintage cars designed to run on leaded petrol.

What does engine knocking sound mean? ›

Knocking occurs when fuel burns unevenly in your engine. When everything is going as it should, and the cylinders have the correct mix of air and fuel, the mixture burns in a controlled, progressive manner. After each cylinder's air/fuel mixture burns, it should create a small “shock wave” in your engine.

Can knocking damage an engine? ›

Severe knocking can lead to catastrophic failure in the form of physical holes melted and pushed through the piston or cylinder head (i.e., rupture of the combustion chamber), either of which depressurizes the affected cylinder and introduces large metal fragments, fuel, and combustion products into the oil system.

Is engine knocking an easy fix? ›

Engine knock isn't always the easiest car problem to repair. Here are a few of the most common solutions to knocking issues. Timing belt replacement: Most smaller cars, including most four-cylinder sedans, will use a rubber belt to regulate and control your engine's timing.

What are two effects of knocking in engine? ›

Knocking can cause overheating of the spark-plug points, erosion of the combustion chamber surface, and rough, inefficient operation.

How long will a knocking engine last? ›

Once an engine starts to knock, the rod can fracture without warning. It could be the next time you start it in your driveway, or it could keep going for six months. Eventually though, the engine will blow and you'll be stranded somewhere.

What damage can engine knock cause? ›

This can cause severe engine damage. The reason why you are hearing knocking is that the pistons are knocking against the crankshaft walls. If left unrepaired, you will damage the crankshaft and render your engine inoperable.

How long will an engine last after it starts knocking? ›

Once an engine starts to knock, the rod can fracture without warning. It could be the next time you start it in your driveway, or it could keep going for six months. Eventually though, the engine will blow and you'll be stranded somewhere.

Can adding oil fix engine knock? ›

Adding more oil will make the noise go away, but it won't solve the underlying cause of the noisy engine – the oil leak.

Can thicker oil stop engine knocking? ›

No. First off, there are different things that can be called knocking, so I'll have to go through those. But none of them will be cured by thicker oil. If it's detonation (often called knocking or pinging), different oil won't help.

Does a knocking engine need to be replaced? ›

Once you confirm the faulty components, you must get them repaired or replaced in some scenarios. Determining whether it's worth fixing engine knocking depends heavily on the overall repair costs compared to your vehicle's value.

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