Car Makes a Rattling Noise When Accelerating

Worn-out suspension components, a misaligned driveshaft, broken or loose heat shields, and low transmission fluid can all cause a rattling sound when accelerating. Some fixes to these problems are simple, like tightening loose parts and topping off the fluid level, while others might require more expertise to diagnose and repair.

Driving down the road and hearing a rattling noise when accelerating can be a scary experience. While some rattling sounds can result from serious issues, the culprit is often minor enough for you to fix yourself.

Possible causes of a rattling noise when accelerating

Rattling noises when accelerating your car can be concerning. If you experience this issue while driving your car, it’s best to identify and fix it quickly.

Many things can cause a rattling sound in your vehicle, but these are the most common causes you’re likely to encounter.

Broken or loose heat shield

A broken or loose heat shield is one of the most common causes of a rattling sound in cars. These critical parts protect your vehicle’s components from excessive heat.

The heat shield surrounding the catalytic converter is infamous for becoming loose or detaching. This is partly due to the catalytic converter’s position close to the ground.

There are also heat shields around the car engine bay and exhaust manifold. If these heat shields malfunction, you might notice your car overheating or developing a burning smell.

Damaged suspension components

Damaged or worn-out suspension components are a frequent cause of rattling noises. Shocks and struts do not last forever, so you’re likely to experience a bumpy or noisy ride when they go bad.

If you have damaged suspension components, you will probably also experience uneven tire wear, and your car may pull in one direction.

Worn-out wheel bearings

Worn-out wheel bearings are another common cause of rattling noises when accelerating. These parts allow your car’s wheels to turn smoothly, and if they go bad, they can cause various problems.

Your vehicle might have bad wheel bearings if your tires shake and wobble as you accelerate or the tread wears unevenly.

The exhaust system is insecure or worn out

Faulty or worn-out exhaust components are classic causes of rattling sounds in vehicles. Your car’s exhaust pipe and muffler sit close to the ground, which subjects them to corrosion and damage from road debris.

Loose exhaust components may also cause rattling noises and are frequently caused by faulty exhaust hangers. These are small rubber parts that occasionally break or become disconnected.

The driveshaft is out of alignment

Your car’s driveshaft is what transfers the power from the transmission to the rear axle, allowing the wheels to turn. If the driveshaft is out of alignment, it can cause your car to shake and handle poorly.

If your vehicle has a misaligned driveshaft, you might also notice uneven tire wear and a rough vibration when accelerating.

Worn-out piston

Another cause of rattling and engine noise is piston slap. Piston slap occurs when the piston knocks or rattles against the engine cylinder wall.

If your car has worn-out pistons, you may have a check engine light on, experience decreased engine performance, or have poor gas mileage.

Engine accessory problems

Engine rattling isn’t always the result of internal problems. External engine components, like drive belt pulleys and tensioners, can malfunction and cause a rattling or squealing noise.

You can test for these issues by removing the drive belt and starting and gently revving the engine. If the sound goes away, there’s likely an issue with one of these components.

If you try this method, be careful not to run your engine too long without the belt. It is responsible for supplying power to essential parts, like the alternator, power steering pump, and water pump.

Valve train problems

Problems with the valve train can also cause rattling sounds. This is usually caused by worn-out intake and exhaust valves, as well as faulty hydraulic lifters.

Bad valves can cause your car to prematurely combust the fuel, which results in a noise like glass bottles knocking together. Faulty hydraulic lifters might cause the valves in your engine to get stuck and make a clicking or knocking noise.

Bad motor mounts

Motor mounts are a type of bushing that connects your engine to the car’s frame and absorb some of the bounces and shocks while driving. If your motor mounts fail, the engine will shake excessively and could damage other components.

You’ll likely notice a rough shaking from the engine bay while driving, as well as squeaking, rattling, or vibration sounds. Additionally, bad motor mounts can cause throw your car out of alignment, leading to uneven tire wear.

You might also notice engine oil leaks or a check engine light if you have bad motor mounts.

Low transmission fluid

Transmission fluid is essential as lubrication for the gears inside your vehicle’s transmission. If the fluid level is low, your car may struggle to shift, and the transmission might rattle, shake, or overheat.

Some additional signs of low transmission fluid include slipping gears and a jerking feeling when accelerating.

Key TakeawayRattling noises when accelerating can be caused by a number of issues, including damaged or worn-out suspension components, bad wheel bearings, low transmission fluid, loose heat shields, and faulty engine components.

How to fix a rattling noise when accelerating

Now that you have a better idea of what might cause a rattling noise when accelerating, you might be wondering how to fix these issues.

These projects vary in difficulty, but with the right guidance, you should be able to complete them yourself.

Fix the heat shield

If a loose heat shield is causing a rattling noise in your car, you’ll need to secure it. This is a relatively simple job; you only need to follow a few steps.

Step 1: Raise your car using jacks or ramps. Then, crawl under the car and locate the loose or damaged heat shield.

Step 2: Tighten the screws connecting the heat shield to your car. If the screws are missing, you can replace them with new ones or use wire to reattach the shield.

If your heat shield is severely damaged or corroded, you may need to replace it with a new one.

Repair the suspension system

If you determine that your suspension is causing a rattling noise, you’ll need to figure out which part is faulty and repair it.

Step 1: Lift the car with ramps or a jack and jack stands.

Step 2: Replace any damaged components. These parts may include struts, shocks, coil springs, sway bars, control arms, and tie rods.

Step 3: Tighten all components to the proper torque specifications. Then, test-drive your vehicle at a low speed to ensure the suspension handles well before building speed to listen for any noises.

Diagnosing the problem may require a mechanic’s expertise, and your car will need an alignment after replacing any suspension component.

Make sure the motor mounts are tight

Engine rattling can be the result of loose engine mounts. While these mounts occasionally need to be replaced, you can often resolve the issue by tightening the bolts that secure them to the vehicle’s frame.

Step 1: Park your car safely and turn the engine off.

Step 2: Disconnect the car battery’s negative cable.

Step 3: Locate the engine mounts—there are usually three or four. Use a wrench or ratchet to tighten the bolts until they are snug. Do not over-tighten the mounts.

Step 4: Turn the car on and check the engine mounts by putting the vehicle in gear, holding the brake, and lightly revving the engine. Bad motor mounts will cause the engine to lurch and shake when this is done.

Realign the driveshaft

If your car’s rattling noise comes from the bottom or middle of the frame, and a vibration accompanies it, you might need to realign the driveshaft.

Step 1: Use a jack and jack stands or ramps to raise the vehicle off the ground.

Step 2: Go under the car and locate the driveshaft. It runs from the transmission to the rear differential.

Step 3: Remove the driveshaft by unscrewing the bolts that connect it to the transmission and differential.

Step 4: Inspect the driveshaft and locate the markings (either a dimple or arrows) that illustrate how to orientate the shaft. Alternatively, you can align the driveshaft by ensuring that each half is positioned with the serial numbers facing the same direction.

Step 5: Line up the markings on both halves of the driveshaft.

Step 6: Reinstall the driveshaft by tightening the bolts to the manufacturer’s torque specifications.

You can do this in your driveway. However, if you don’t correctly align the driveshaft or incorrectly tighten the connectors, you can cause further damage and worsen the issue. If you’re not confident in your ability to align the driveshaft, it’s best to take your car to a professional.