What Causes Rattling Noise When Accelerating?

Cars are fine-tuned machines with several components that work in harmony for optimal operation. If any of these components fail, become loose, or malfunction, it’ll affect the overall performance.

For example, a rattling noise when accelerating means one or more components are loose or damaged. And it is dangerous to drive a vehicle that is not running as it should. In this article, I’ll explain the causes of rattling noise when driving and how to fix rattling noise when accelerating. But first, let’s start with the possible causes.

Common problems causing rattling noise when accelerating

If you hear a rattling noise when accelerating, it is ideal to identify and address it, though it can be challenging to identify the problem. The issue can result from several factors, such as faulty water pump bearings, dirty or low engine and transmission oil, loose suspension or engine components, and more.

Faulty engine mounts

Engine mounts connect your engine to the car frame and keep it stationary. It is made of rubber and metal parts, which can wear out over time. If the mount is damaged, it won’t keep the engine stationary. Instead, the engine will dangle and come in contact with other parts in the engine bay when you move or stop—invariably making a rattling noise.

Broken heat shield

Exhaust manifolds and pipes are the hottest parts of a car. Because of the heat they emit, manufacturers cover them with heat shields to prevent the heat from damaging other car parts.

Over time, the heat shield can become loose or broken. If any of this happens, the shield will dangle as you drive, causing a rattling noise. If the front end rattles when accelerating, you could have a broken heat shield in the engine compartment.

Low engine oil

Believe it or not, the engine oil is as important as the engine itself because you can’t drive without it. If the oil becomes low, it’ll not circulate to every nook and cranny part of the engine, especially to the valve train. If this occurs, the reciprocating parts of the engine will rub against each other, causing a grinding or rattling noise.

Poorly lubricated transmission

The transmission is as important as the car engine. Without it, the vehicle cannot move. However, it must be adequately lubricated to function as it should. If there’s low fluid in the transmission, the gears and other parts inside the tranny will rub against each other, and you will hear a transmission rattling noise when accelerating.

If you ignore this rattling noise for an extended period, it will cause catastrophic damages and drop expensive repair bills on the table.

Damaged valve train

One of the most prevalent causes of rattling noise when accelerating and check engine light on the dashboard is issues in the valve train. The valve train consists of several components like valve springs, valves, pushrods, retainers, camshafts, tappets, and rocker arms.

If any of these components are damaged, it’ll cause a rattling noise once you start the engine. However, the noise will become louder or more noticeable as you accelerate the engine.

Loose timing chain

If you hear a slapping or rattling noise from the engine bay, especially at the front of the engine, you likely have a loose timing chain. The timing chain is what synchronizes the camshaft with the crankshafts together. Over time, as the engine runs, the timing chain will become stretched or worn. If you suspect you have a loose timing chain, have a certified mechanic check it out.

Worn-out exhaust parts

The exhaust system consists of several parts that work together to reduce exhaust noise and makes the toxic exhaust gas less harmful before sending them into the environment. If any of these components fail, break, or wear out, it will cause dampening in the exhaust system, which could lead to rattling noise as you drive. These exhaust components include;

How do you identify and fix rattling noise when accelerating?

Identifying and addressing rattling noise at an earlier stage will not only save you from embarrassment, but it’ll also save you money and further damage. Here are the simplified ways I use to identify and address rattling noise when accelerating. Follow the same guidelines if you are experiencing this issue.

Inspect and fix broken heat shield.

My rule of thumb is to start with the easiest-to-fix and common causes of a problem when running a diagnosis. Since a broken heat shield is easy to fix and a common cause, start by inspecting it to see if it is the leading cause. Inspect the bolts holding it and see if the shield is broken.

If loosened bolts are the cause, tighten them properly. If the shields are broken, bind them with copper wire or replace them with new ones.

Inspect and replace worn exhaust components.

The second thing I usually check is worn-out exhaust components. But before you touch any exhaust components, let the exhaust cool down to avoid burning off your hand. Get a lying mart and slide under the vehicle to check worn exhaust components. Inspect the exhaust components for rust, corrosion, worn-out parts, and disconnected clamps.

Reconnect disconnected clamps, apply exhaust tape on areas with small holes, and fix large holes with aluminum and epoxy. Meanwhile, it is best to replace damaged components.

Inspect and fix transmission issues.

As explained earlier, low fluid is a common cause of transmission issues. Check the transmission fluid and ensure it is at the right level. Top the fluid if it is below the recommended level.

Typically, adding more fluid is all you need to fix the problem if low fluid is the cause. However, if the tranny has been running with low fluid for a long time, it may have caused other issues in the system. In this case, topping the fluid will not rectify the rattling noise. You’ll have to contact a mechanic to disassemble the tranny and replace faulty components.

Inspect and replace the defective engine mount.

Ask an assistant to start the vehicle and put it in gear. Inspect the engine mounts as he puts the vehicle in gear. If you can’t tell whether the mounts are bad or okay, ask him to put the vehicle in reverse or drive and accelerate the engine with the brake pedal depressed to the floor. If the mounts are damaged, the engine will feel as if it’s bouncing off.

The best way of fixing a defective engine mount is to replace it. So, if the inspection proves the mount is bad, get a new one and replace it.

Inspect and fix defective valve train.

If the rattling noise comes directly from the head cylinder, open the head cylinder cover and inspect the valve train components. But first, check the engine oil and confirm it is at the right level. Low engine oils usually cause a rattling noise in the head cylinders.

If the motor oil is low, top it to the recommended level and see if that will fix the problem. Open the head cylinder cover and inspect the valve train components if oil is not the problem. This is best left for gearheads to inspect because you may not notice a lousy valve train component unless the damage is obvious. The mechanic will replace any defective component to address the rattling noise.

Contact a professional mechanic.

If the timing chain feels loose or stretched as you remove the head cover, contact a professional mechanic to inspect and address the issue. This task is left to professionals unless you know your onions in the field.

How much does it cost to fix a rattling noise when accelerating?

There’s no specific answer to this question because several factors can be the root cause of the problem. For instance, if low engine oil is the leading cause, you can top up the oil or do an oil change between $50 and $75. But if a stretched timing chain is the culprit, budget $400 to $1,500 to replace it. Therefore, fixing a rattling noise when accelerating could cost as little as $50 or as high as $1,500.

Can low transmission fluid cause a rattling noise?

The transmission relies on the tranny fluid to lubricate and cool the internal parts. If there’s no or low transmission fluid, internal parts like planetary gear sets, clutch packs, and others will rub against themselves. If this happens, the transmission will make a rattling noise until you add oil. However, ignoring the noise for an extended period will cause catastrophe in the transmission.

Can a timing chain rattle when accelerating?

If your timing chain, belt, or timing tensioner loses its strength or becomes stretched, it’ll play more than it should. This leads to a clattering or rattling noise as you accelerate the vehicle. You can also hear the noise on idle, but it’ll become obvious as you accelerate the car.

This symptom can also happen when there is low engine oil or issues with the valve train. Therefore, it is essential to run a thorough diagnosis before blaming any component.

Do cars rattle when low on oil?

The purpose of the engine oil is to lubricate and cool internal engine parts. If the oil becomes low, it’ll not effectively carry out this responsibility. As a result, the reciprocating engine parts will start to move harder against each other, causing friction and grinding. When friction and grinding occur, the engine emits knocking, rumbling, clicking, and rattling noise.

How long will a rattling timing chain last?

A rattling chain can break in as little as 1,000 miles and can go as far as 10,000 miles. It all boils down to how old the chain is and why it rattles. However, you should always fix the timing chain rattling noise as soon as possible because it can cause catastrophic engine damage and leave you stranded on the road.

Final Words

Several factors, like defective valve train components, worn-out exhaust components, broken engine mounts, and broken heat shields, can cause a rattling noise when accelerating. Meanwhile, the easiest way to address the noise is to identify where the noise is coming from. 

For instance, rattling noise when accelerating at low speed could be due to low transmission fluid or low engine oil, and rattling noise when idling is caused by a broken heat shield or worn-out exhaust component. Follow the simplified guides above to track and address the rattling noise.