Catalytic Converter Leak – How to Repair It in Simple Steps

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A catalytic converter leak shouldn’t give you a headache. You can patch the hole using a suitable gasket sealer, which can last several months and allow you time to find a permanent solution. Catalytic Converter Leak This article has discussed the details below and mentioned a nearly permanent option to deal with a significant leak without replacing the converter. You will also discover how to identify a failing cat so you can act before things get out of hand.

How To Mend an Exhaust Leak on Your Catalyst?

To mend an exhaust leak on your catalyst, locate it and patch it up with a gasket sealer that can withstand high temperatures for a long time. If the leak is significant, use a mesh as reinforcement or consider welding for a longer-lasting solution. A cat is a critical component of a modern car’s exhaust system. It helps to minimize the pollutants in the exhaust fumes. A leak can significantly reduce efficiency, emitting toxic gasses into the atmosphere.
Also, an exhaust leak before catalytic converters will impact engine performance. Modern engines use sensors to determine when the vehicle outputs too much gas emissions and activates limp mode. That’s a security feature that reduces speed and turns off essential functions when the engine detects a problem. Therefore, a leaky cat is something you can’t ignore. Age is one notorious cause of leaks in cats. Over time, the cat’s body wears out and breaks down. As a result, cracks and holes can develop, allowing gasses and fumes to escape. Improper installation can also cause exhaust leaks. Whatever caused the leak on your cat, it’s essential to know how to address the problem, even if it’s temporary. A cat replacement is one of the most expensive repairs; you probably aren’t ready. So, here’s how to catalytic converter patch:
  • A hydraulic floor jack and jack stands (check how to use them here)
  • Some soapy water in a spray bottle
  • A suitable exhaust system sealer, e.g., Meeco’s Red Devil 110
  • A small, soft wire mesh
  • Ceramic exhaust tape (or fiberglass tape, aluminum foil tape, basalt tape)
  • Jack Up Your Vehicle

You need to access the vehicle’s underside, where the cat is. Therefore, jack up the car and secure it on jack stands. After that, locate the converter. It will be between the exhaust manifold and the muffler. Jacking Up Vehicle For those who want to know, “What does a catalytic converter look like?”, it’s almost similar to an exhaust silencer or muffler. The only difference is that cats are slimmer. As mentioned, cats are placed close to the engine to help them warm up quickly and start to function immediately. You can skip step 2 below if you already know the leak location.
  • Locate the Leak

Turn on the engine and feel around the cat for exhaust gas leaking. You may need someone to help accelerate the vehicle to make the task easier. While the car accelerates, be keen to notice intermittent hissing or popping catalytic converter leaking sound. You can also spray soapy water on and around the cat; bubbles will form at the leak spot. Once you identify the leak, please turn off the engine and allow it time (at least 2 hours) to cool. Note that the exhaust pipe can get extremely hot. Working on the vehicle while hot is a risk you want to avoid.
  • Patch up the Leak

With the vehicle cooled, put a reasonable amount of the exhaust system sealer onto the leak. You’ll have to push and spread the product with your finger and ensure it’s flush with the cat to properly seal the hole. After that, allow the sealer enough time to dry before starting the engine. As mentioned, the cat and exhaust can get very hot – up to 1,200 degrees Fahrenheit. So, it would be best to have a sealer that can withstand such high temperatures. Many DIYers use Meeco’s Red Devil 110 gasket cement and stove sealer. However, it’s a temporary solution because it can only last a few months at best. Some people have also used VersaChem Exhaust joints and crack sealer. It’s said to resist the high heat of the exhaust fumes and hold the leak fine for several months, which is better than paying for a new cat. You can’t use JB weld on the cat or anywhere on the exhaust pipe, as it can’t hold up to more than 500 degrees Fahrenheit. That means it would melt away in minutes and expose the leak again. For a big hole, there are several ways to deal with it, depending on your budget. One uses the gasket sealer and a wire mesh. The mesh will provide structure, then apply the sealer and allow it time to completely dry. If it’s done right, you can also have your cat welded to provide a more permanent solution. Welding the cat is typically a job that requires advanced tools and the skills of a professional. The labor cost starts at $75. Note that sometimes the leak may not be on the cat directly; it might be at the joints or on the exhaust manifold. You can use ceramic exhaust tape, which can resist high temperatures of up to 2,282 degrees Fahrenheit. You can also use fiberglass, aluminum foil, or basalt, commonly used in high-heat, sealing, gasketing, and thermal insulation around ovens, furnaces, and hot pipes. Ceramic tapes are more resilient to high heat and have a longer life. Note that silicone sealants aren’t recommended because they may not handle temperatures beyond 700 degrees Fahrenheit. They can quickly burn if used to seal the cat or any component on the exhaust system. As the sealants burn, they usually form a silicone film on the oxygen sensor (catalyst poisoning). As a result, the sensor may send inaccurate data to the ECM, leading to an improper air-fuel ratio inside the engine.

How To Know When Your Vehicle Has a Catalyst Problem?

To know when your vehicle has a catalyst problem, consider the tell-tale signs, including performance issues, ruined fuel economy, and physical damage. The rattling sound coming from the vehicle is one of the notorious symptoms of a leaking cat. A problematic cat will also trigger the check engine light.
  • Performance Issues

“Does catalytic converter affect acceleration?” Yes, if the cat develops a problem, you’ll also notice different issues with the engine. They include poor acceleration (sputtering) or problem starting, which usually means “catalytic converter clogged.” A clogged cat prevents a smooth flow of exhaust gasses. In other words, it ‘suffocates’ the engine and prevents it from exhaling the exhaust. Car Performance Issues In most cases, replacing a clogged cat (catalytic converter sluggish acceleration) is the solution. However, depending on the extent of the problem, fuel additives can help flush out deposits and restore their efficiency. If you have a clogging issue, try that catalytic converter cleaner and see what happens.
  • Weird Smells and Sounds

A sulfur or rotten egg smell from your car is one common symptom of a contaminated cat. The sulfur smell indicates the cat cannot convert H2S (hydrogen sulfide) to sulfur oxide. You may also notice an ammonia (NH3) smell, which means compromised catalyst function. Bad cats are also likely to produce a rattling noise, particularly if they have a leak problem. If you notice such noise while the engine is running, know that your cat is broken and needs fixing.
  • Physical Damage

Sometimes you don’t have to wait until your cat’s problems are manifested through the vehicle’s performance. When you check the cat and see its housing warped or discolored, there may be an internal issue such as overheating or leaking. In other words, physical damage (one of the overheated catalytic converter symptoms) is a sure sign that your cat is nearing its end and should be a cause for concern. Thus, be keen to notice things like a bent, broken part or anything odd-looking and act as soon as possible.
  • Failing Emissions Test and Terrible Gas Mileage

As stated, the primary purpose of the cat is to reduce emissions that vehicle exhaust releases into the atmosphere. Failing the semi-annual or annual emissions test might indicate a failed or dying cat. Poor fuel efficiency can indicate an exhaust issue with your car. That may happen when the cat is clogged, pushing some exhaust back into the engine. The consequence of that is poor performance and compromised fuel economy.
  • Malfunction Indicator Lamp (MIL) On

The MIL might turn on for different reasons. However, it may indicate an issue with your exhaust system. Suppose the ECM (engine control module) detects a problem with your cat. In that case, it may return a DTC P0420 on an OBD2 scan tool, meaning the cat’s efficiency is below the threshold. Seek help from a mechanic if the CEL turns on and doesn’t have a scan tool to diagnose the problem. Malfunction Indicator Lamp Note that a cat leaking fluid (specifically dripping water or steam) doesn’t indicate a mechanical problem. It means that the component is doing its job correctly, and there is no need to contact your mechanic. However, watching your exhaust to timely notice any signs of oil fouling is essential. A bluish tinge from your vehicle’s exhaust may indicate an oil leak. That can clog the cat’s honeycomb if it’s not taken care of immediately. Also, the MIL could indicate an open loop, meaning the engine is running too lean or too rich. Either way, your cat would be in danger. Thus, act fast whenever the warning light illuminates.

How To Increase Your Catalytic Converter’s Lifespan?

To increase your catalytic converter’s lifespan, avoid parking your car for prolonged periods. Drive it often and take a few highway trips occasionally. Most importantly, keep up with regular vehicle maintenance, such as oil and air filter changes and EGR valve check-ups. Cats are made to last the entire life of the vehicle. However, sometimes your cat may break internally or meltdown, necessitating a replacement. And as mentioned, that’s one of the most expensive repairs. Therefore, knowing how to care for this vital component is essential to prevent premature failure by following the tips mentioned above; see more detail below.
  • Drive the Car

Avoid parking your car for weeks without driving it. Vehicles like to be driven. Short drives aren’t good enough. Ensure you take a few long trips once in a while. For example, spending about 30 minutes driving on the highway at least once a week is essential to allow the vehicle to reach its proper operating temperature.
  • Keep Up With Regular Maintenance

Regular maintenance, such as inspections and oil and air filter changes, will address many issues that can damage your cat. You must also routinely check your engine’s exhaust gas recirculation (EGR) valve. The valve recirculates some exhaust gasses into the engine to optimize combustion and ensure optimal fuel economy. Car Regular Maintenance The EGR also helps keep combustion temperatures low to minimize the toxic substances your vehicle produces. If the EGR fails, the combustion temperatures will rise, leading to a hotter exhaust. That high heat often ends up melting the inside of the cat. An inefficiently working EGR valve can also damage hoses and cause the cat to clog or leak.

Can the Same Fix for a Catalytic Converter Leak be Applied to Leaking Transmission Cooler Lines at the Radiator?

When dealing with a fix for leaking transmission cooler lines at the radiator, it is important to note that the same solution applied to a catalytic converter leak may not be effective. It is advisable to consult a professional to accurately assess the extent of the issue and determine the appropriate course of action to fix leaking transmission cooler lines.


Now you know how to stop a catalytic converter leak, whether big or small. We will leave you with a summary:
  • To fix a leaky cat, apply a suitable gasket sealer to seal a small hole.
  • You can weld your cat to seal a leak permanently.
  • Common symptoms of a bad cat include sluggish acceleration, unusual noises and smells, and physical damage.
  • Regular maintenance can help to increase your cat’s life.
You’re now well-informed on how to deal with the problem at hand – a leak on your cat. So, gather the tools and solve the issue!
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