5 Reasons Why Your Car Is Making a Knocking Noise When Coasting (And How to Fix It Yourself)!

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knocking noise when coasting

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Coasting disengages the vehicle’s wheels from the engine and allows it to travel by momentum or gravity. While some car’s coasting saves fuel, it also allows you to listen to your car with the engine quieter. You may hear different types of noises, including knocking noises.

When you hear knocking noise when coasting, your car’s bearing and wheel nuts may be the culprits. It may also be the hand brake drum and CV joints to blame. To pinpoint the exact cause, diagnose the vehicle further or seek professional help.

If your vehicle has knocking noises, I have compiled the possible causes and solutions for this issue.

knocking noise when coasting

Possible Reasons for Knocking Noise When The Vehicle Coasts

In the following section, I have listed the possible reasons you hear knocking noises when the vehicle coasts.

1. Wheel Bearing Issues

Wheel bearing issues are one of the possible reasons behind the knocking noises when your vehicle is coasting. Wheel bearings allow a connection between the non and moving parts of the vehicle.

Bearings wear due to reduced lubrication, mostly after a leak. The bearing issues can be on any wheel and may be behind the knocking noise back left wheel of the car.

Wheel-bearing issues turned out to be the cause for this Reddit user.

Solutions

The solution to wheel bearing issues causing the knocking noises is to replace the faulty bearing. However, this is usually a complex job that is better left to the professionals.

Nevertheless, if you have the required expertise, you can change it by following the steps below.

Step 1

Place the vehicle on an ideal flat surface

Step 2

Loosen the lug nuts to the wheel with failing bearings

Step 3

Raise the car with the jack and support it with the stands

Step 4

Remove the wheel

Step 5

In some models, you’ll need to remove the brake assembly

Step 6

Remove the old wheel bearing

Step 7

Grease the new wheel bearing and install it

Step 8

Replace the brake assembly if you removed it earlier

Step 9

Replace the wheel and lower the vehicle

Step 10

Tighten the lug nuts using a torque wrench

Step 11

Test for noises

Cost For Fixing

Replacing a single-wheel hub is around $350 (national average), though the price may vary with the vehicle’s type.

2. Loose Wheel Nuts

Loose wheel nuts are another possible reason that most users ignore only to find it as the cause. Take the example of one seat and Cupra community member who had this issue only to find a loose wheel nut as the cause.

If you recently serviced or changed the wheel, you may have tightened the nuts loosely. When loose, the nuts will make the knocking sounds and are more audible when coasting due to the reduced engine noise.

To pinpoint this as the source of the noises, check all the wheels for loose wheel nuts.

Solutions

The solution to a loose wheel nut is to tighten it to the ideal torque. Consult your user manual to learn the required torque and use a torque wrench to tighten the nut.

However, you can also consult the torque settings for wheel nuts pdf for specs for some popular cars and models.

3. Hand Brake Drum Issues

Another possible reason behind the knocking noises is the hand brake drum issues. The hand brake drum helps decelerate the vehicle once the brake shoes or pads press against it.

One of the most likely issues with the hand brake drums is if there are worn or damaged brake shoes. When these parts are damaged or worn, they may not retract fully and will continuously contact the drum. This continuous contact will create the knocking noises you’re hearing.

Hand brake drums may also be behind the clicking noise when decelerating.

Solutions

The solutions to hand brake issues to replacing the failing part. In this case, the brake shoes. Get the ideal brake shoes for your brake and follow the steps below.

Step 1

Loosen and remove the wheel nuts and jack up the car

Step 2

Remove the wheel

Step 3

Remove the axle-bearing nut with a ratchet

Step 4

Remove the drum

Step 5

With pliers, remove the brake shoe springs

Step 6

Unscrew the holdout spring on the shoe

Step 7

Remove the old brake shoes

Step 8

Spray the drum brakes

Step 9

Install the new brake shoes

Step 10

Install the brake shoe holdout springs

Step 11

Reinstall the brake shoe springs

Step 12

Replace the drum and reinstall the axle-bearing nut

Step 13

Reinstall the wheel and tighten the nuts to the necessary torque

Step 14

Test the vehicle for noises when coasting

Follow the video below for visual aid.

4. Loose Exhaust

Another possible reason you hear these knocking noises when coasting is a loose exhaust. Again, the sound is more audible when coasting due to the reduced engine sounds.

Exhaust pipes can become loose due to failed mounts. A loose exhaust pipe can knock on the surroundings as the vehicle runs, making sounds.

To confirm this is the issue, check the exhaust system for play. Also, you can jack the vehicle and observe for any loose mounts or bolts, to confirm the as the source.

Solutions

Depending on your type of exhaust and the reason behind the issue, you may need to weld or replace the loose screw. Follow the steps below for this solution.

Step 1

Jack the vehicle

Step 2

Locate the loose mount or bolts

Step 3

Weld the loose mount and attach the exhaust pipe

Step 4

In case of a missing bolt, replace the bolt and fasten it tightly

Step 5

Test the vehicle to see if you hear the knocking noises when it’s coasting

5. CV joint

It may catch you as a surprise that I added Constant Velocity joint as a possible cause for the issue. This is because CV joints are known to make noises when turning, especially at low speeds.

However, worn CV joints can cause this issue when coasting, even if you’re not turning. For instance, a user in a short video (Listen to the noises) solved the knocking noises by replacing CV joints. Take a look!

Solutions

The solution is to replace the CV joints. Follow the steps below.

Step 1

Get the replacement CV joint

Step 2

Set the vehicle to park

Step 3

Loosen the wheel nuts and jack up the vehicle

Step 4

Remove the wheel

Step 5

You may need to remove brake calipers and rotors

Step 6

Using a pry bar, detach the CV joint from the wheel hub or axle

Step 7

Remove the retaining rings and remove the CV joint from the axle

Step 8

Install the new CV joint and secure it with the necessary rings or springs

Step 9

Reassemble brake rotors or calipers if you’ve removed them earlier

Step 10

Replace the wheel and tighten it

Step 11

Lower the vehicle and test for noises

Cost For Fixing

The steps will vary with the vehicle type. If a professional handles these repairs, expect to pay at least $300 for a single joint.

Final Thoughts

Any noise when you drive is enough to cause you concern. In this case, when you have knocking noises when coasting, ensure the wheel nuts are well tightened. Afterwards, check other issues I have covered in the article and apply the necessary solutions.

Most of the solutions are easy to do at home if you have the necessary tools and expertise. However, consider hiring a professional if you’re uncomfortable handling them. Also, use quality parts to avoid near future issues on the part.

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