Have you ever been driving down the street, when all of a sudden you hear a strange knocking sound coming from your car? It can be really unnerving, especially if you don’t know what’s causing it.
But don’t worry – you’re not alone. Many drivers experience this same problem, and often have no idea what to do about it. The first step is to understand what exactly causes this knocking sound.
There are a couple of reasons why you might be hearing a knocking sound coming from under your car. Some of the most common ones are – low octane fuels, failing knock sensors, worn bearings, excess carbon deposits, faulty spark plugs, and/or issues with the timing chain. All of these issues can be resolved with proper maintenance and taking your car in for regular servicing.
In this article, we’ll give you an in-depth explanation of each of these possible causes, and what you can do to fix them. We’ll also discuss a few other car noises you might be hearing, and how to troubleshoot them as well.
So, if you’re ready to get to the bottom of this knocking sound, read on!
Contents
1. Low Octane Fuel
Octane refers to the measure of a fuel’s ability to withstand compression in an engine without ‘exploding’ or ‘knocking.’ The higher the octane number, the greater the fuel’s resistance to knocking.
If your vehicle is designed to run on high-octane fuels, and you’re using a lower octane fuel, it can cause knocking. This is because the lower octane fuel ignites too early in the combustion process, which results in the ‘knocking’ sound.
Solution: Read your vehicle’s owner’s manual to find out what octane rating of fuel it requires and make sure you’re using the right type of fuel for your car. Don’t opt for cheaper gasoline just to save a few bucks – it’s not worth it in the long run.
2. Failing Knock Sensor
A knock sensor is a sensor that’s located on the engine block, cylinder head, or intake manifold of the car. The purpose of this sensor is to sense engine knocking or pinging and send a signal to the engine control unit (ECU). The ECU will then adjust the ignition timing to reduce or eliminate the knocking noise.
If your knock sensor is failing, it can cause lead to false alarms, which then lead to knocking sounds. This is because the ECU isn’t receiving the correct signal from the knock sensor, and therefore can’t adjust the ignition timing properly.
Solution: The best way to fix a failing knock sensor is to replace it. You can do this yourself if you’re mechanically inclined, or take it to a professional mechanic. For standard economy vehicles, replacing the knock sensor can cost anywhere between $120 to $500.
3. Worn Bearings
Worn bearings are another common cause of knocking noises. Bearings are what allow the engine’s moving parts to rotate smoothly. This is especially true for rod bearings, which is what allows for smooth piston movement.
If your bearings are worn, your car’s pistons can rattle against the crankshaft, which will cause a knocking noise. This is usually more pronounced when you first start your car, or when you’re idling.
Solution: To fix this problem, you’ll have to install new bearings. Depending on the severity of the damage, you might also need work done on the pistons and crankshaft. This is a pretty big job, so we recommend taking it to a professional mechanic. You should also keep in mind that this work takes time, so don’t expect it to be done quickly.
4. Excess Carbon Deposits
This is perhaps one of the most common causes of knocking noises. Carbon deposits can build up on the valves, piston rings, and injectors over time. When this happens, you’ll most definitely hear knocking sounds while driving. This is because the carbon deposits can prevent the valves from sealing properly, or cause the piston rings to lose their tension.
Solution: Most good-quality fuels will have detergents that will help prevent carbon deposits from building up. If you’re using low-quality fuels, try switching to a higher-quality fuel. You can also add a fuel injector cleaner to your tank every 1500-3000 miles to help keep parts of the fuel system clean. In case you’re still facing the issue, the problem might be with your engine itself taking in more fuel than it needs (thus leading to excess carbon deposits), in which case you’ll need to take it to a professional mechanic for assessment.
Our recommendation for some great fuel injector cleaners:
5. Faulty Spark Plugs
The role of a spark plug is to create a spark that ignites the air/fuel mixture in the engine’s cylinders. Although it’s quite a small component, it’s essential for the proper functioning of your engine.
If your spark plugs are worn out or damaged, they can’t create a strong enough spark to ignite the air/fuel mixture properly. When this happens, all the fuel will not get ignited properly, and the fuel that did not get ignited will eventually catch fire and detonate. That’s when you’ll hear a knocking noise.
Solution: The only way to fix this problem is to replace the spark plugs. Usually, this is done every 30,000 miles, but it can vary depending on the make and model of your car. You can replace them yourself or take it to a professional mechanic (it’ll cost you around $200-$250).
6. Issues With the Timing Chain
The timing chain is responsible for synchronizing the rotation of the crankshaft and camshaft, thus ensuring the proper timing for the engine’s valves to open and close. Whenever you’re using your car’s engine, the timing chain is also in use, and that’s why it’s a very important component.
Excess slack in the timing chain can cause it to create a knocking or even rattling sound. This is often seen when you cold start your vehicle, and the oil pressure and oil flow are at their lowest. However, in severe cases of wear and tear to the timing chain, the sound can continue even when the engine is at operating temperature.
Solution: The best way to fix this problem is to replace the timing chain with a new one. Usually, this is done between 80,000 and 120,000 miles under normal circumstances. This is a big job, and we recommend taking it to a professional mechanic.
Other Common Car Sounds That Might Mean There’s a Problem
Although ‘knocking’ sounds are the most common, there are other sounds that might indicate there’s a problem with your car. If you hear any of these sounds, we recommend taking your car to a professional mechanic for an inspection:
Squealing
Affected Area – Serpentine Belt
If you ever hear a squealing sound upon starting your vehicle, it’s most likely an indication that the serpentine belt needs to be replaced. The serpentine belt is responsible for powering the engine’s accessories (e.g., the alternator, air conditioning compressor, etc.), and if it’s damaged, it can cause all sorts of problems.
Replacing the serpentine belt is a relatively simple and inexpensive job that can be done by most mechanics.
Squeaking
Affected Area – Power Steering
A squeaking or squealing sound (especially when turning the steering wheel), it means that there’s an issue with the hydraulics in your power steering system. Basically, the power steering requires fluid to function properly, and if there’s a leak in the system, or if the fluid level is low, it causes air to get into the system, which then causes the squeaking/squealing sound.
It’s important to get this problem fixed as soon as possible because power steering problems can lead to much bigger issues down the road.
Droning/Humming
Affected Area – Tires
If you hear a droning or humming noise while driving, it’s most likely an indication that your tires are old and worn out. The sound is even more prominent if the tires are worn unevenly. Sometimes, this can also happen if your tires are underinflated.
Immediately check your tires’ tread depth and pressure levels to see if that’s the problem. If not, then it’s probably time for a new set of tires.
Loud Bang
Affected Area – Engine
You might have definitely heard the sound of a car backfiring at least once. It’s a very loud bang that comes from the engine, and it’s usually caused by an issue with the ignition system. When fuel is ignited in the cylinders, it sometimes doesn’t all burn up. The unburned fuel will then ignite all at once when it finally reaches the exhaust system, and that’s what causes the loud bang.
If your car is backfiring, we recommend taking it to a professional mechanic for an inspection. Although it’s not really an emergency per se, it does mean that your engine is not running as efficiently as it should, and this can lead to further problems in the long run.
Roaring
Affected Area – Exhaust System
Roaring sounds (especially while accelerating the vehicle) means that there’s an issue with the exhaust system.
Car engines are extremely loud, and that’s why cars come equipped with a muffler. The muffler’s job is to dampen the noise coming from the engine. If there’s a crack or leak in your exhaust system, hot gases will escape before they reach the muffler. This will make your car much louder than usual.
If you hear a roaring sound coming from your car, we recommend taking it to a professional mechanic for an inspection. Not only is it annoying, but it can also be dangerous if the exhaust gases (carbon monoxide specifically) are leaking into the cabin of the vehicle.
Basic Car Maintenance Tips That Every Driver Should Know
Now that you know what some of the most common car sounds mean, it’s time to learn about some general maintenance tips that every driver should know. By following these simple tips, you can help keep your car in tip-top shape and avoid costly repairs down the road:
- Familiarize yourself with your car’s user manual: Your car’s user manual is full of valuable information that can help you maintain your vehicle properly. It contains everything from the recommended tire pressure levels to the type of oil that should be used.
- Check your car’s fluids regularly: Every car has a variety of different fluids that need to be checked on a regular basis (e.g., engine oil, power steering fluid, brake fluid, etc.). These fluids are responsible for keeping your car’s various systems running smoothly, so it’s important to make sure that they’re always at the correct levels.
- Inspect your tires regularly: Your tires are one of the most important parts of your car, and they need to be inspected on a regular basis. Check the tread depth and pressure levels at least once a month.
- Have your car serviced regularly: Even if you’re the most diligent driver in the world, there are some things that can only be inspected and/or fixed by a professional mechanic. That’s why it’s important to have your car serviced on a regular basis. This will help ensure that any potential problems are caught early on.
- Learn what the warning lights mean: Most cars nowadays have a variety of different warning lights that come on when there’s an issue. It’s important to familiarize yourself with these lights so that you know what they mean and can act accordingly.
- Check your brakes: Your brakes are one of the most important safety features on your car, so it’s important to check them regularly. Inspect the pads and rotors at least once every 6 months or every 10,000 miles.
- Clean the air filters: The air filters help keep your car’s engine clean and running smoothly. Over time, they can get clogged up with dirt and dust. That’s why it’s important to clean them on a regular basis (usually every 12 months or so).
- Replace damaged windshield wipers: Most drivers don’t think about their windshield wipers until they need them. But it’s important to replace them when they get damaged or worn out.
- Make sure to have insurance: If you’re involved in an accident, insurance can help cover the cost of repairs. It’s important to make sure that you have the right type and amount of coverage for your needs.
- Wash your car regularly: This goes without saying, but a clean car is a happy car. Not to mention, it’ll help you avoid rust and other damage that can occur from dirt and grime build-up.
Keeping these 10 tips in mind will help you keep your car running smoothly for years to come.
Is It Safe to Drive a Car With a Knocking Engine?
While it is possible to drive a car with a knocking engine for quite some distance, it’s not advisable. A knocking engine is an indication that there is something wrong with the engine and it should be checked by a mechanic as soon as possible. The sooner you fix it, the less expensive it’s going to be.
Final Thoughts
Being a car owner comes with a lot of responsibilities. But if you’re diligent about taking care of your car, it’ll take care of you in return. Hopefully, some of the things that we’ve covered in this article will help you understand your car a little better and give you the confidence to take care of it properly.
As always, if you have any questions or concerns, don’t hesitate to reach out to us. We’re always happy to help!