Catalytic Converter Rattle: Symptoms, Causes and Permanent Fixes

A catalytic converter is part of your car’s exhaust system. It turns pollutant gases into less harmful and safer emissions. Over time, your catalytic converter wears out or becomes faulty and it can start ratting.

When a catalytic converter rattles, it is an indication that something is not right under the hood of your car. If a loose heat shield causes the rattle, you should tighten the bolts. If the rattle results from the building up of residue, reduce it using cleaners, additives, and high-octane fuel.

The rattling of the catalytic converter can also be a sign that your car needs service. Some symptoms will show you that your catalytic converter requires service.

Do you want to learn the signs that your catalytic converter requires service and know what it means when the catalytic converter rattle?

This article will give you all the signs and how to stop it.

why is my catalytic converter rattling

Your catalytic converter rattles because of the loose heatshield  striking the cab floor. Alternately, the internal honeycomb structure may get clogged or damaged, resulting in a loud noise.

Fragmented Honeycomb

Over time, the ceramic honeycomb structure of the catalytic converter is prone to damage. You probably crushed and shattered it accidentally while driving, causing the broken parts to rattle.

Alternately, the high temperatures within the converter can cause the honeycomb-like structure to crack, which may be audible when the various components of the converter move. In rare instances, the heat may even fuse honeycomb parts or get clogged by buildup.

If there is a fault with the honeycomb structure, you may be in trouble, as honeycomb problems are far more harmful than heat shield problems. Issues with the structure can cause engine problems and severe damage to your vehicle; thus, they must be repaired as soon as possible.

Loose Heat Shield

Every catalytic converter is equipped with a heat shield to protect the vehicle’s floor from the intense temperatures generated by the converter. Without it, the heat may be sufficient to melt.

Typically, the heat shield is attached with screws; with time, the screws may loosen, rust, or even break off. This will result in the heat shield touching the vehicle’s floor as you drive. If the rattling is worse as the car accelerates, there is likely something loose in the exhaust system.

A loose heat shield by itself is not extremely hazardous. However, driving with it may lead it to grow loose and finally fall off; therefore, you need to fix the faulty heat shield as soon as possible to avoid worsening the problem.

Other Noises?

A faulty catalytic converter may make sounds other than rattling. It is crucial to understand what these sounds indicate to be aware of your cat converter’s maintenance.

These sounds consist of:

  • Ticking noise: this noise can be heard while the cat is burning oil, gasoline, or coolant. It may also be the result of a leak in the converter. It is frequently audible during cold starts, acceleration, and idling.
  • A pinging sound typically indicates blockage due to excessive use, age, or fuel contamination.
  • A leak or a loose shield frequently causes the knocking sound.
  • Popping noise is often caused by a blockage in the converter, which restricts exhaust flow and causes back pressure.

Catalytic Converter Rattle Symptoms

There are unique elements located under the hood of your car for helping your vehicle perform properly; a catalytic converter is one of those components.

It is an essential element for your car’s exhaust system. If it has a problem or is wearing out, it is best to take it for service.

So, which are the signs to look out for that will tell that your catalytic converter needs service?

Here are the key symptoms;

Rattling Noise

When your catalytic wears out or has a fault due to fuel mixtures, the honeycombs inside starts to collapse or break apart, causing rattling to occur.

The residue also builds up and causes blockage or cracks, breaks, or collapses of the ceramic. The cracked ceramic pieces make a rattling noise.

After turning your car on, you may notice that the noise gets even worse when you leave the problem unattended for a more extended period.

The noise also becomes louder, and you will hear it when you accelerate. The rattling will cause poor engine performance, dark and smelly exhaust pipes and sometimes the check engine light starts coming on.

Reduced Engine Performance

A catalytic converter that is clogged, blocked, or clogged makes it hard for the engine to expel exhaust, thus affecting the engine’s performance adversely.

Your car might start delaying acceleration when you start it from a standstill. The performance begins declining when you try going uphill, it starts struggling, or you notice it has less power.

It is frustrating and also very dangerous when your engine has poor performance.

Check the exhausting force and flow to test if your catalytic converter is the issue. You should park the vehicle in the park and have a helper to help push the accelerator down to run the engine at around 2000 pm.

Now put your finger near the tailpipe to feel the force, amount, and heat expelled from the exhaust. If you notice the heat is light, meager, or hot, your catalytic converter has an issue.

Engine Misfires

If you have been using a very rich fuel mixture, the raw fuel can sometimes enter the catalytic converter and then ignite. The engine misfires can cause overheating of the catalytic converter.

Therefore, engine misfires are a result of backpressure from a catalytic converter that is failing, hence causing damage to the converter.

When the converter is clogged, it restricts the flow of oxygen needed for the engine’s combustion process. When the combustion is not taking place properly, it coats the sparkplug with residue and causes them to misfire.

When engine misfires occur repeatedly, it affects fuel efficiency and causes damage to the engine.

So, if your car has engine misfires, take it to an expert to check it out without driving for long distances.

Check Engine Light Turns On

If your car’s computer senses a fault in the catalytic converter, the check engine light will illuminate to signal you that there is a problem that needs to be checked by an expert.

The oxygen sensors around the catalytic converter send information to the EMC, which helps to compare the oxygen amount in the exhaust system. If the numbers do not match the correct parameters, the check engine light turns on.

If you notice illuminating of the check engine lights, then there could be an issue with the converter.

However, it is essential to note that the check engine light might illuminate because of other reasons in the engine.

So, ensure you get a skilled mechanic to scan and diagnose the code accurately so that you can know the cause precisely.

Lower Gas Mileage

If your catalytic converter is failing, it decreases the gas mileage due to combustion issues and reduced engine performance.

The efficiency of fuel drops because the engine struggles to expel exhaust due to a damaged or blocked catalytic converter.

It will cost you more to travel the same distance due to excellent fuel consumption.

At the same time, the engine will experience difficulty when starting due to a faulty converter which causes the engine to get extra fuel in the chamber.

Increased Emissions

When the catalytic converter has a fault or has failed, it becomes difficult to clean the exhaust system.

So, when the darkening of the exhaust system increases, it is a sign that the catalytic converter is not functioning correctly.

In this case, if an emission test is done in your car, it is likely to fail because the catalytic converter is not functioning correctly.

Clogged Converter

If your fuel mixture is incorrect or the exhaust system has a problem, it clogs the catalytic converter.

When the catalytic converter is clogged, it causes many issues with the functioning and performance of your car.

Unfortunately, it might be hard for auto mechanics to diagnose the problem of the catalytic converter without having to replace it, which might be very costly.

Catalytic Converter Rattles when Accelerating

The catalytic converter will rattle when you start accelerating because the ceramic honeycomb in the catalytic converter is broken.

The rattling can also happen over some time because the catalytic converter is physically damaged due to direct impact.

Unfortunately, it is not possible to fix the honeycomb, but there can be a simple solution.

You can tap on the catalytic converter with a hammer until you get exactly where the rattle noise comes from. Now, put a screw into the catalytic converter on that spot. The screw will penetrate the honeycomb and hold it in the correct position. It will have solved the rattling issue but only temporarily.

Please note that this is not a permanent solution but is a way to help you drive some extra miles.

How to Stop Catalytic Converter Rattle

Do you want to quiet your rattling catalytic converter?

Here are methods to help you fix the issue and save on replacing a catalytic converter.

1. Clean Your Catalytic Converter

Cleaning your catalytic converter might seem like a simple method, but it is one of the best and easiest methods to restore your catalytic converter.

It is crucial to clean it because building up residue overtime in the catalytic converter might block airflow and cause noise hence poor performance.

Therefore, this method is perfect for restoring your catalytic converter without spending too much to replace it.

2.Use High Octane Fuel and Fuel Additives

If you have been using the lowest octane gas, run a few tanks of high octane gas in your car. It will likely increase the flow of air and stop the rattle.

In addition, you can get fuel additives to help you clean the catalytic converter when you add them to your gas tank.

3.Use Lacquer Thinner

Cleaning your catalytic converter with lacquer thinner is an efficient and easy method to apply. Here, you require one gallon of lacquer thinner to your fuel tank, which has 10 gallons of gasoline.

Now drive your car for 150 miles and ensure the RPMs are about 2500 or more for at least 30 minutes.

After the lacquer thinner has functioned through your car’s system, you will have improved performance, and it will also quiet the rattling.

4. Use Sodium Hydroxide

Here, you remove the catalytic converter from the car and soak its inner side with a spray bottle. Ensure you have sprayed into the catalytic converter from all sides.

Then let the catalytic converter sit for about 20 minutes to ensure the chemicals have enough time to work.

After soaking the substances, you can wash and rinse them thoroughly from both sides.

5. Fix Your Catalytic Converter Heat Shield

If the heat shield becomes loose or misses some bolts, it will cause excess noise when the car is running.

Remove the heat shield by first opening a few bolts to fix this problem. You will require penetrating oil because high heat causes the bolts to be challenging to remove.

Now wash the catalytic converter with water and soap. Before installing the heat shield back, add an anti-seize compound on the bolts and tighten them properly.

6. Replace the Catalytic Converter

Replacing a catalytic converter can be very costly. So, it is best to ensure you purchase a catalytic converter that fits your car perfectly but not a universal catalytic converter.

The best thing about a catalytic converter made specifically for your vehicle is that it comes with bolts and does not require welding.

The first thing is to let the bolts soak in penetrating oil to be easy to remove them. The process of installing a catalytic converter is straightforward.

You should set the catalytic converter in place, and then you insert all the bolts; ensure you add anti-seize compound to every bolt first. Twist the bolts down to the correct torque specification.

Although it is a simple process, replacing the catalytic converter on your own will save you those extra dollars compared to taking it to a repair shop.

7. Regular Inspection of the Engine and Tune-Ups

It is vital to make it a habit of inspecting and maintenance of your car regularly. It would be best to take your car for oil changes and air filter changes more often.

Also, ensure you inspect for any cases of oil and coolant leakages to ensure they do not build up and damage your catalytic converter.

It is important to note that you should inspect your car if the check engine light comes up for proper diagnosis. It will save you more trouble and prevent any adverse damages to your catalytic converter and the engine.

How Long Does a Catalytic Converter Last?

A standard catalytic converter usually has a lifespan of at least 10 years. However, these components are typically constructed to survive the vehicle’s lifetime. Of course, this is not always the case. In some instances, catalytic converters fail prematurely owing to engine performance issues, while others deteriorate with time. Catalytic converters may also be damaged by road debris striking them from the outside (iron or large rocks).

The greatest approach to prolong the catalytic converter’s lifespan is keeping your vehicle in good running condition.

Catalytic Converter Replacement Cost

Is it costly to replace a catalytic converter? What is the cost of a catalytic converter?

What is the Replacement Cost of a Catalytic Converter?

As with any automobile repair, the cost of cat converter replacement varies by car model. The cost to replace a damaged catalytic converter ranges between $945 and $2475. Some luxury cars’ catalytic converters replacement costs could be higher.

In addition to the expense of the actual replacement, you must consider diagnostic expenses and any complications that may result from the failure. For instance, you may need to simultaneously replace the oxygen sensors, the muffler, and the tailpipe. Before beginning the repair, you will need a comprehensive cost study. It may cost more to repair than the vehicle itself.

Final Thoughts

When your catalytic converter rattles, it is a sign warning that there is a problem under the hood of your vehicle. If the rattling results from the loose heat shield, you should tighten the bolts. When the rattle noise is caused by residue building up, you can reduce it using cleaners, additives, and high-octane fuel.

However, if the rattling results from blocked or broken ceramic monoliths, the best option is to replace the catalytic converter. When you replace the catalytic converter, you will prevent more damages to the engine and your vehicle.

In addition, always ensure you take your vehicle for maintenance and proper inspection. It will prevent more damages and make sure you cut extra expenses in the future. Ensure you also see an expert if your check engine light comes up for the proper diagnosis.

I hope you now understand the catalytic converter better, its maintenance, and the right time for replacing it.


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