How to Clean a Catalytic Converter: Tips and Tricks

Can You Clean a Catalytic Converter? Here’s What You Need to Know

Before discussing a few ways you can try to clean a catalytic converter, I have to remind you that these devices, by their very nature, are self-cleaning. Their very job is to clean your exhaust. So, when you get a P0420 or P0430 trouble code, it’s because the catalytic converter isn’t working properly. You can try to clean it, but “being dirty” isn’t the root cause. Something is causing it to fail at its job. I’ll explain how that happens below. I’ll cover the two ways to clean a catalytic converter, but unless you fix the underlying problem that caused it to fail, it will set the same trouble codes again. Cleaning a catalytic converter, if it works at all, is a temporary fix. It may get you past an emissions test, but it won’t last.

Is your catalytic converter a candidate for cleaning?

Catalytic converters fail in four ways:

1) An oil, soot, or carbon coating on the surface of the honeycomb that prevents the catalytic reaction from taking place. You might be able to clean off some of this coating, but unless you fix the underlying problem, it will set a trouble code again.
2) A melted or clogged substrate caused by overheating, melting, or cracking. There is no way a cleaning can reverse this damage.
3) A poisoned substrate due to the introduction of silicone or coolant. In most cases, cleaning won’t reverse this.
4) Impact damage from hitting a rock or parking curb. Cleaning can’t fix this.

In other words, of the four ways a catalytic converter can fail, only the first one might be fixed by cleaning.

How to check your converter to see if it’s a candidate

Get under the vehicle and perform a visual inspection. Then, using a rubber mallet, tap the underside of the converter and listen for any signs of rattling. If you see any of the signs below or experience a loss of power when driving, cleaning won’t fix your problem

• Overheating: The steel exterior has blue-purple shading,
• Signs of impact damage
• Makes a rattling noise if you tap the bottom with a rubber mallet

Overheated catalytic converter viewed from the outside. This converter will not benefit from cleaning. It must be replaced

Impact damage. This converter will not benefit from cleaning. It must be replaced

Inside view of catalytic converter with a melted or broken ceramic structure. This converter will not benefit from cleaning. It must be replaced

The two ways to clean a catalytic converter

1) With a pour-in-cleaner like Cataclean or CRC’s Guaranteed to Pass or
2) Remove the catalytic converter and wash it using the method listed below. This kind of manual cleaning aims to remove soot and baked-on oil carbon buildup so the precious metals can be exposed to the exhaust and start working again. That makes sense in theory. However, it ignores two important points: 1) High levels of soot can scrub off the microscopic layer of precious metals, so the cleaning just exposes a bare ceramic substrate once it’s removed, and 2) A catalytic converter operates in the 700°F to 1,400°F range, so it’s not as easy as you think to remove the baked on contaminants.

How the pour-in catalytic converter cleaners work

Theoretically, the solvents in catalytic converter cleaners can loosen and dissolve some soot/carbon build-up that may reduce airflow or efficiency. Keep in mind that all pour-in products get burned during combustion, so the conversion of these chemicals into other vapors does the actual cleaning.

Cataclean

In the case of Cataclean, the Kerosense, Toluene, Xylene, Hexanol, Isopropanol, and Acetone solvents convert into carboxylic acid, active peroxy oxides, and aldehydes. In some cases, they can clean off the carbon coating. Chemical cleaners may not be enough to dislodge solid carbon for severe clogging, especially when you consider that most of the cleaners are burned during combustion.

CRC Guaranteed To Pass

CRC Guaranteed To Pass, on the other hand, uses petroleum distillate as the carrier and Polyether amine (P.E.A) as the cleaner. P.E.A. is the same cleaner used in Top Tier fuel and is specifically designed to dissolve carbon buildup in fuel systems.

I’ll list the contents of both of these cleaners at the end of this article.

Step-by-step Guide To Manually Clean your catalytic converter by removing it and using cleaners

The biggest mistake DIYers make when using this method is to rush the process. This is an all-day job. Remember, this coating is baked onto the structure, so it takes a long time to remove it, and circulating the cleaning solution is critical to its success. If you skip the pump circulation, you may as well skip the entire process.

Tools and Supplies you’ll need to clean your catalytic converter

• A pump and hoses
• 5-gallon bucket
• Concentrated degreaser
• Dawn PowerWash Cleaner
• 15 gallons of distilled water
• Compressed air
• Heat gun

1) Remove the oxygen sensor from the catalytic converter and then remove the converter from your vehicle
2) Mix the degreaser with 2.5 gallons of distilled water in the bucket to achieve the highest concentration of degreaser. This will remove oil and carbon buildup and surface soot.
3) Place the catalytic converter in the bucket.
4) Place the pump’s suction hose at the bottom of the bucket and the outlet hose at the top of the catalytic converter
5) Circulate the degreaser/water mix through the catalytic converter for 2 hours. Then flip the converter and repeat for another 2 hours.
6) Dump the degrease/water solution and rinse the converter with a garden hose
7) Repeat the cleaning process using Dawn Power Wash Cleaner and distilled water using the same method ( 2 hours, flip, and then another two hours).  This will remove all degreaser residue and continue to clean any remaining buildup that’s able to be removed.
8) Dump the soapy water solution.
9) Rinse out the pump and wash the bucket.
10) Fill the bucket with the remaining distilled water and use the pump and hoses to rinse the converter, flipping it several times to rinse all the soap off all the surface areas.
11) Use compressed air to blow out all remaining water
12) Use a heat gun to dry the interior.
13) Reinstall on your car and let it idle to dry the insulating material.
14) Then take it for a test drive

Cataclean Catalytic Converter Cleaner Formula (from their patent)

Kerosene about 8 parts by volume
Toluene about 12 parts by volume
Xylene about 40 parts by volume
Hexanol about 2 parts by volume
Isopropanol about18 parts by volume
Acetone about 20 parts by volume
The entire mixture should be added to the fuel in 32 parts to the fuel volume

CRC Guaranteed To Pass Catalytic Converter Cleaner

The CRC Guaranteed To Pass cleaner takes a different approach than Cataclean. Their Material Safety and Data Sheet (MSDS) shows

Petroleum Distillate25-35%

Don’t just soak the converter. Circulate the cleaner through the converter using a pump and hoses.

Sweetened middle petroleum distillate 25-35%
Polyether amine (P.E.A.) (Proprietary_ 25-35%

©, 2021 Rick Muscoplat