5 Reasons Why Your Car Makes A Knocking Sound When Braking

When a knocking sound is heard when braking, it can be quite alarming. There are many causes, but only a few are common and worth diagnosing. 

Why does my car make a knocking sound when I brake?

The five common causes of a knocking sound when braking includes loose bolts or bearings, loose brake calipers, faulty shock absorbers, damaged rotor disks, and loose or worn-out brake pads. We recommend also checking the fluid levels and tires when hearing a knocking sound. 

We have dealt with the issue of a knocking sound when you press the brake pedal working with cars in the past, and it can result in severe damage if not addressed immediately. 

We will explain all of the common causes for why a car makes a knocking sound when braking and the best fixes below. 

Knocking Sound When Braking? 5 Common Causes

Car brakes are a safety feature that is used to stop the vehicle and avoid collisions. The braking system comprises many parts, including brake pads, brake drums, brake shoes, and hydraulic fluid.

However, a knocking noise when braking is a common concern for drivers. It is usually a sign of problems with the braking system or relevant parts under the hood. 

Below are the five most common causes for why someone may experience a knocking sound when braking. Keep these in mind and how we would approach fixing the issue. 

Loose Bolts And Bearings

When a car makes a knocking noise when braking, it may be because of loose bolts and bearings. This is a common problem in older cars that have not been maintained. 

This can cause an unbalance with the wheels while driving, and knocking occurs when using the brakes. The loose bolts and bearings might need to be tightened or replaced.

When a car is braking, the brake pads squeeze against the rotors. The pressure of the pads creates friction, which slows down the vehicle. This is what makes a car stop.

If there is too much play in the bearings or bolts, it will cause them to make a knocking sound when they are pressed against each other.

Loose Brake Calipers

The brake caliper holds the brake pads and pistons. It acts like a clamp on the wheel’s rotor to stop the wheels from spinning smoothly. When using the brakes, it will apply pressure to create wheel friction. 

When they come loose, braking becomes less stable, and it can cause a knocking sound when braking due to the friction between two surfaces rubbing together.

A loose caliper will also cause one side of your car’s braking system to work harder than the other, leading to uneven wear on your tires and uneven stopping distances.

Faulty Shock Absorbers

Shock absorbers are not just for comfort but also for drivers’ safety. If the car has faulty shock absorbers, drivers can experience a knocking sound when braking.

This is because metal-to-metal contact happens, and this will result in damage to your brake pads and rotors as well as your tires. It’s also a more distinct sound when driving over rugged roads and bumps. 

A faulty shock absorber may not be able to absorb the impact of the car’s body weight and the weight of the passengers when braking. The car will then bounce up and down and make a knocking sound.

Damaged Rotor Disks

Damaged rotor disks can also cause a knocking sound while braking on a car. The brake pads are in contact with the rotor disks during braking, so uneven contact is not ideal. 

The friction between them causes a knocking sound to be heard. This causes them to wear out faster over time while making a distinct knocking noise. This is also why rotors need to be replaced periodically.

Loose Or Worn Brake Pads

Another common cause of this problem is that the brake pads are worn out and need to be replaced or tightened. This common issue can also impact the vehicle’s braking accuracy and ride comfort.  

Brake pads wear out because they are made of metal and rub against the rotor when you apply pressure on the brakes. Brake pads are relatively cheap and easy to replace when they finally go bad. 

How Do You Fix A Knocking Sound When Braking?

After considering the five most common causes for a knocking sound when braking, it’s time to learn how to fix the problem after determining what’s wrong. Follow the steps below to take care of the issue promptly. 

Check The Tires

A few things can happen with the car tires that may cause a knocking sound while braking and accelerating. This can be uneven tread wear, bad alignment, a broken belt, or bad bolts and bearings. 

This is why we recommend checking the tires first. Eliminating this as a potential cause means something is likely wrong with the actual brakes.  

Look At Fluid Levels

Another thing that might be causing the brakes to make noise when using them would be if the brake fluid level were low. Remember to check the fluid levels and see if this quick fix can solve the issue. 

Brake fluid needs to be updated and filled every 12-24 months, depending on how much a car uses. 

Check Brake Calipers And Brake System

The next thing that needs to be done is to check the brake calipers and the brake system to see if they are the reason for this knocking sound. It might be a simple fix that doesn’t require a visit to a local mechanic. 

Loose calipers can quickly be tightened because of the bolts that hold them in place. We recommend using a thread cleaner or a new bolt if it seems the current one is worn. 

Inspect The Suspension

A worn suspension will also cause a knocking sound. This should be investigated because when the suspension fails, it can be an expensive repair. 

Driving a car with a bad suspension is also uncomfortable and dangerous. 

Bring The Car To A Professional

Lastly, we always recommend visiting a local professional or mechanic to anybody with little to no experience under the hood of a car. They can diagnose and fix the issue much faster, depending on the problem, and it can be cheaper. 

Key Takeaways

• The most common causes for a knocking sound when braking are loose bolts or bearings, loose brake calipers, faulty shock absorbers, damaged rotor disks, and loose or worn-out brake pads.
• When the knocking sound occurs while braking, start by checking the tires and fluid levels too. If the tires are uneven, worn, or loose, they can make noise; the same is true for low brake fluid levels. 
• We recommend consulting with a professional to handle most issues with the brakes because a knocking sound can lead to more serious damage.