Rattling Noise When Idle (Key Causes & Fixes)

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Geoff Cudd

Geoff Cudd

I am a serial entrepreneur and a consumer advocate. When I’m not helping car buyers, I love working on ventures that have a positive impact.

I run a cause marketing agency and serve on the board of Vayu Global Health where we are disrupting the medical industry and preventing the needless deaths of mothers and babies during childbirth.

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It's annoying to hear a rattling noise when idle, making your ride incredibly uncomfortable. Car rattling can occur for several reasons and factors. And if left unattended, it can result in a severe issue, which can cost thousands of dollars to fix.

If you hear a rattling noise in your car when idle, you must contact a forensic mechanic to identify the cause of the noise.

Failing motor mounts, bad catalytic converter, low oil level, loose engine heat shield, and bent pistons and timing chains cause rattling noise when idle.

In this article, we will discuss everything you need to know about rattling noise in a car and what to do about it.

Car Making Rattling Noise When Idle Video

Rattling Noise When Idle

These are several reasons why your car might experience rattling noise when idle:

1. Loose Engine Heat Shield

One of the most common reasons car rattling can occur is the loose heat shield.

Since the heat shield is made from various materials, such as aluminum foils and sheets, it can rust easily, which can cause the screws to become loose. This can cause the heat shields to flap and make noise.

2. Failing Motor Mounts

These components are designed to keep the engine in place and prevent metal parts from touching each other.

Usually, these mounts are made from rubber to prevent vibrations and damage. If the motor mounts fail, it could indicate something is wrong with the system.

3. Bad Catalytic Converter

If your car's catalytic converter is missing or not fitted properly, it could cause a sound. This component is made from ceramic-like materials and can get damaged if it gets bad.

4. Low Oil Level

Another common reason car rattling can occur is the low oil level.

Although most people don't realize this, low oil levels can cause vibrations in certain engine parts. It's essential to check the oil level to ensure it's complete regularly.

5. Bent Pistons or Timing Chains

Another common reason car rattling can occur is the damage or loosening of the transmission or clutch.

This can cause vibrations that can create noise inside the vehicle. If you're experiencing this issue, contacting a mechanic is essential to diagnose the problem.

Rattling Noise From Inside the Car

One of the most common ways to diagnose a problem is by moving from simple fixes to bigger ones.

For instance, if you notice a loud and unsettling sound when your engine is running, it's essential to rule out the simple fixes as the cause of the issue. Doing so will allow you to avoid costly repairs later on.

Even though modern cars are much better than their predecessors, they still have issues that can cause interior noise.

These include damaged glove box hinges, an open center console cover, and a cup holder resting on the door panel. So, inspecting the interior is essential if you hear a loud and unsettling sound while your vehicle is idle.

Some cars have cargo-carrying systems that could be the source of the issue. These can cause a loud and unsettling sound while your vehicle is idle.

Generally, these problems can be fixed by removing the cargo cover or using a pair of pliers and a screwdriver.

Rattling Noise From Under the Car

If you're still unable to determine the source of the issue, the noise may be coming from other parts of the car.

For instance, if you cannot find any loose interior components, the problem may come from the vehicle's under-the-car portion.

One of the most common reasons car noises can occur is the emissions and exhaust systems.

If you're experiencing this issue, it's essential to consider the less expensive repairs first.

Heat shields are typically cheap and can protect nearby areas from the heat coming from the exhaust system. However, if they get damaged or worn out, they can start to cause a loud and unsettling sound.

If the car's exhaust system is damaged or corrupted, it can cause a loud and unsettling sound. Sometimes, a loose part of the exhaust system can cause a rattle. A failing catalytic converter is another issue that can cause a loud and unsettling sound.

This component is vital to the car's exhaust system, removing harmful elements and compounds from the exhaust gasses.

Its core is similar to a honeycomb, and it can transform unburned gasses into harmless components in scorching conditions.

As the core of the catalytic converter gets damaged, it can cause small pieces to drop off and eventually cause the housing to crack.

If this happens, you must replace the catalytic converter to prevent it from stopping working properly. In addition, doing so will allow you to avoid having your vehicle fail a smog test.

Rattling Noise From Under the Hood

If you're still experiencing this issue, the noise may come from other car parts. For instance, if you cannot find any loose interior components, the problem may come from the vehicle's under-the-car portion.

A failing hydraulic valve lifter is one of the most common reasons car noises can occur. This component is a small part that's responsible for opening and closing the engine's valves.

Due to the complexity of today's vehicle valve systems, many cars have variable valve timing.

In older cars, hydraulic lifters often collapse and produce a loud and unsettling sound as they fail. If this issue is the cause of your vehicle's noises, you must replace all of its hydraulic lifters.

A distinct "clack-clack" sound while starting your car could signify a serious issue called a piston slap.

This condition occurs when the gap between the cylinder wall and the piston grows larger, preventing the piston from moving correctly.

If this issue is the cause of your vehicle's noises, you must replace all of its hydraulic lifters.

Can Low Oil Cause Rattling?

A low oil level can also cause your car to make a loud and unsettling sound. This issue can occur when the temperature in the engine is high, which will allow the vehicle to suck more air into the oil pan.

However, if the car's not getting enough oil, the air can get sucked in and cause the vehicle to noise.

What to Do if You Hear Rattling Noises When Idle

One of the most important factors to consider when experiencing car noise is that it could indicate something is wrong with your vehicle. But, on the other hand, it could be a simple and easy fix if it's not a severe issue.

However, if it's still not a serious issue and you still hear a loud and unsettling sound, you must take the car to a mechanic.

Since there are many possible reasons why your car might make noise while idle, it's essential to have it serviced by a car mechanic as soon as possible.

Getting your vehicle to a garage is the best way to fix it. This facility can provide a professional mechanic who can thoroughly inspect and repair your car if something is wrong.

Rattling Noise When Accelerating

It might be a little unsettling to hear a loud clicking sound as your car accelerates.

However, since your vehicle isn't designed to produce noise other than exhaust and engine noise, it's essential to investigate what's happening.

Although low engine oil might cause some car noises, it's also possible that something more serious is happening.

Common reasons triggering car noises include poor engine mounts, a damaged flywheel, and loose interior trim.

Can Bad Spark Plugs Cause Rattle?

Yes, it can. If your car's spark plug is defective, it might be time to replace it. A loud and unsettling noise from the engine might indicate that it needs to be replaced.

Other Causes of Rattling Noise in a Car

These are some other causes of rattling noise in a car:

1. Cracked or Broken Serpentine Belt

All gasoline or diesel cars have a serpentine belt. This component has a function that allows it to drive various components, such as the air conditioning compressor, water pump, and the electrical components of your engine.

The difference between a timing belt and a serpentine belt is that the former is usually hidden, while the latter is visible.

If the serpentine belt gets broken, your car will start making noises, and you might have to call a towing truck. Also, if the water pump stops working, your car might overheat.

2. Broken Flexplate

A flex-shock or flexplate is a component that can improve the smooth running of a car by connecting the engine's crankshaft to the torque converter.

If your car has a broken flexplate, this connection between the converter and the crankshaft might not work correctly, and it might cause your vehicle to start making noises.

If this happens, you might have to remove the flex plate cover and inspect for missing or cracked bolts.

3. Broken Crankshaft Harmonic Balancer

The harmonic balancer is a component that can reduce the vibrations from the engine by absorbing and reducing the effects of the rotation of the crankshaft.

If the metal and rubber on the harmonic balancer get dislodged or worn out, it might cause engine vibrations. This component is an essential part of your car and might eventually fail.