Catalytic Converter Cleaning: How to Deep Clean Vehicle’s Catalytic Converter

As an ASE-certified master technician, one of the most common issues I encounter involves contaminated catalytic converters. Over years of use, these vital emissions components become internally fouled, restricting exhaust flow and causing reduced performance.

Key Take Away

Fortunately, a thorough deep cleaning can often remove the accumulated carbon, oil residue, and other gunk to restore catalytic converter efficiency. Cleaning your converter can help stave off expensive replacement costs.

This meticulously researched guide will teach you how to effectively clean a restricted catalytic converter. I cover:

  • Evaluating symptoms of a clogged converter
  • Selecting the optimal chemical cleaner
  • Step-by-step application instructions
  • Tips to improve effectiveness
  • Assessing results and re-treating if needed
  • Preventing future contamination
  • Professional cleaning alternatives
  • FAQ and consumer guidelines

Armed with this information, you can take action to clean your catalytic converter and get your vehicle running cleanly again.

Key Takeaways on Cleaning Catalytic Converters:

  • Allow the engine to fully warm up before applying cleaner to open pores.
  • Properly locate the actual catalytic converter inlet pipe before treating.
  • Remove any heat shields or covers blocking access to the converter.
  • Thoroughly clean exterior converter surfaces before cleaning to allow flow.
  • Use a catch pan beneath the inlet pipe to capture the used cleaner.
  • Empty the cleaner into the inlet so it thoroughly penetrates the converter.
  • Let the cleaner actively dwell for 10-15 minutes minimum to work.
  • Flush dissolved deposits out using pressurized air.
  • Properly reinstall components and shields when complete.
  • Wear protective equipment like goggles and gloves for safety.
  • Retreat if symptoms like smell and low MPG remain.
  • Prevent recontamination by fixing leaks and avoiding idling.
  • Consider professional cleaning for extreme fouling.

Understanding Catalytic Converters (Why Cleaning Is Important)

To understand why keeping your catalytic converter clean is so important, it helps first to understand what catalytic converters do and how they work to reduce air pollution:

What is a Catalytic Converter?

The catalytic converter is a crucial emissions control device on all gasoline-powered vehicles manufactured since 1975. It comprises a stainless steel outer housing containing a fragile ceramic honeycomb structure coated with precious metal catalysts.

You’ll typically find platinum, palladium, and rhodium metals in modern catalytic converters as catalysts. As hot exhaust gases from the engine pass through the converter, these metals facilitate chemical reactions that convert toxic pollutants into significantly less harmful compounds.

How Do Catalytic Converters Reduce Emissions?

Catalytic converters reduce pollution in the following ways:

  • Convert carbon monoxide into carbon dioxide
  • Convert hydrocarbon emissions into water and CO2
  • Convert dangerous nitrogen oxides into nitrogen and oxygen gases

When emitted from the tailpipe, these converted exhaust compounds have dramatically less adverse health and environmental impacts.

Catalytic Converter Effectiveness:

When operating correctly, catalytic converters are astonishingly effective at reducing air pollution – typically eliminating over 90% of hydrocarbons, carbon monoxide, and nitrogen oxides in engine exhaust, according to emissions testing by the Environmental Protection Agency (EPA).

However, over years and accumulated mileage, catalytic converters can become fouled and contaminated internally from oil residue, fuel additives, coolant leaks or antifreeze, and carbon buildup caused by engine misfires or excessive idling. This contamination restricts exhaust flow, limits contact with the catalyst metals, and lowers conversion efficiency.

Thorough deep cleaning is required to remove this buildup and unclog converters to restore their full emissions scrubbing functionality.

When Should You Clean Your Car or Truck’s Catalytic Converter?

Cleaning your catalytic converter is strongly advised whenever you notice any of the following symptoms that indicate declining performance and restricted exhaust flow:

  • Illumination of the check engine light accompanied by P0420 or P0430 OBD trouble codes specifically indicating a problem with your catalytic converter converting emissions properly
  • Failure of a state emissions inspection test with the catalytic converter explicitly flagged as not achieving required reductions
  • Noticeable decrease in engine throttle response, acceleration, and overall performance
  • Significant drop in fuel mileage and gas efficiency compared to EPA ratings for your vehicle when new
  • Repeatedly fouled or failing oxygen sensors need frequent replacement.
  • A newly developed rattling noise comes from the underside as the contaminated catalytic converter internals break down and become loose.
  • Strong, pungent sulfur odor arising from the exhaust indicating converter damage

As preventive maintenance, periodically cleaning your catalytic converter every 60,000 miles can also help remove a small gradual buildup of oil, fuel, and carbon deposits before converter performance noticeably suffers.

Choosing the Right Type of Catalytic Converter Cleaner

With the wide range of aftermarket chemical catalytic converter cleaners available these days making varying promises, it’s vital to understand the differences when selecting an optimal product for your specific contamination situation:

  • Cerium oxide-based cleaners are top-rated and effective. When heated, cerium oxide safely breaks down carbon buildup via oxidation and helps scrub away oily residue without harsh solvents that could damage components. Leading brand names containing this active ingredient include 3M, LIQUI MOLY, Wynn’s, and BlueDevil converter cleaner products.
  • Restorative platinum additive cleaners are formulated to replace small amounts of lost catalyst material inside a converter that has declined with age. Replenishing the platinum aids chemical reactions and conversion efficiency.
  • Magnesium/aluminum-based cleaners derived from magnesite and aluminite mineral deposits can penetrate profoundly and lift away heavy carbon buildup through a slow dissolving process as you drive the following application.

It’s wise to avoid highly corrosive, silicone-based, or solvent-only catalytic converter cleaners that provide no protective coatings or performance restoration. Make sure to match the cleaning product carefully to the contamination level your converter is experiencing. Mild surface buildup requires only minor cleaning, while heavily concentrated clogging necessitates more aggressive chemical cleaner potency to penetrate and dissolve away years of residue fully.

Among the top consumer-reviewed and recommended catalytic converter cleaning products are:

  • Wynns Catalytic Converter Cleaner – $15 for 16 oz bottle
  • 3M Platinum Plus Cleaner – $18 for 8 oz can
  • CRC Guaranteed to Pass Emissions Test Formula – $14 for 16 oz can
  • LIQUI MOLY Converter Cleaner – $17 for 300 ml bottle

Based on my professional experience, I recommend using the cerium oxide-based LIQUI MOLY Catalytic Converter Cleaning Fluid paired with their OCAT Oxygen Sensor Cleaner as a complete exhaust system restoration regimen. But any quality name-brand converter cleaner matching your contamination level will provide substantial results.

Steps for Safely and Effectively Cleaning a Catalytic Converter

Once you’ve obtained a quality catalytic converter cleaning product suitable for your vehicle, follow these steps closely for a safe and effective DIY application:

Warm up Engine First

Before introducing any cleaner, let the engine fully warm to the average operating temperature. It opens the pores of any stuck-on contaminants to prepare surfaces for deep cleaning. Stalled or incomplete cleaning attempts from applying solutions too soon can worsen blockages. Allow 10-15 minutes warmup time minimum.

Locate the Catalytic Converter

Carefully identify the precise location of the catalytic converter inlet pipe, typically found just after the exhaust manifold, where it bolts to the underside of the exhaust system near the front of the vehicle. Verify you have located the catalytic converter, not the resonator or muffler component.

Remove Heat Shields

Take off any heat shields or metal covers positioned over the top/sides of the catalytic converter. Allow complete observation of the process and keep shields from inhibiting cleaner flow.

Clean Exterior Surfaces

Thoroughly pre-clean the entire outside housing of the catalytic converter using a degreaser or soap solution and a stiff wire brush. Removing external dirt and grime prevents debris from breaking loose and blocking the inlet pipe when additive flows through.

Position Catch Container

Place a large steel catch pan directly under the converter’s inlet pipe area. It will safely capture any drops of used cleaner you later evacuate to avoid hazardous spills. Avoid placing containers in very hot areas that could ignite spills.

Shake Well and Apply Cleaner

Vigorously shake the bottle of catalytic converter cleaner per the instructions to mix thoroughly. Carefully insert the applicator straw (if included), then slowly empty the ENTIRE contents of the cleaner into the converter inlet pipe with the engine running at 1500-2000 rpm. Let the cleaner fully absorb into the converter brickwork.

Allow Extended Dwell Time

Let the cleaner actively dwell for a full 10-15 minutes minimum to ensure it has time to thoroughly penetrate and dissolve away all the built-up contaminants and restrictions. While waiting, monitor for any smoke or unusual smells from the process. Avoid revving the engine.

Flush Out Deposits

Re-position the catch pan to collect flushed deposits, then use short bursts of pressurized air introduced into the converter inlet to force out the dissolved crud and use cleaner vigorously. Continue rinsing until emissions exiting the converter appear and smell completely clean.

Reinstall Equipment

Once sufficiently evacuated, carefully reinstall any exhaust components, oxygen sensors, or heat shields previously removed before the process. Safely dispose of the drained contaminated cleaner fluid and deposits per regulations. Keep all surfaces meticulously clean.

I strongly advise wearing OSHA-approved eye protection, thick insulated gloves, and long sleeves for maximum safety when performing this cleaning procedure. Never attempt to open up or penetrate the sealed internal converter housing – the ceramic fibers are hazardous if inhaled.

DIY Catalytic Converter cleaner method

While I cannot recommend homemade or DIY catalytic converter cleaners as they lack the potency of professional chemical formulations, here is one potential option if professional cleaning is not feasible:

Exercise extreme caution and research if attempting any DIY cleaning methods.

Homemade Cleaner Possibility:

  • Take 1 cup of lacquer thinner 
  • 1 tablespoon of gasoline (outside, avoid flames)
  • Use 1 tablespoon of liquid dish soap
  • Mix the above ingredients well in an open-top metal container. Allow to dissolve and react for 5 minutes fully.  
  • Follow the safety steps in the article on locating the converter, removing shields, and catching the spilled liquid.
  • With the engine running at 2000 rpm, carefully pour the cleaner into the inlet pipe using a funnel.
  • Allow to soak for 10-15 minutes.
  • Use pressurized air to flush liquid and dissolved contaminants out. 
  • Properly dispose of used liquid. Reinstall equipment. Retreat if needed.

Again, I strongly advise using commercial catalytic converter cleaners over homemade options like the one above. DIY cleaners carry severe risks of fire or explosion from incorrect mixing, cannot match chemical potency, and provide no usage instructions or support. Professional cleaning is best for converters with significant buildup. Please reach out with any other questions!

When Professional Catalytic Converter Cleaning Makes Sense

In severe cases where multiple applications of DIY cleaning using quality chemical converter cleaners have failed to fully restore your catalytic converter to properly functioning like new again, more involved professional ultrasonic or high-heat cleaning may be required before replacing the entire converter unit.

These professional shops that specialize exclusively in catalytic converter cleaning have an array of high-powered industrial equipment at their disposal to thoroughly clean the insides:

  • Highly effective ultrasonic agitation that vibrates loose and dissolves carbon on a microscopic level.
  • They targeted high-velocity heated compressed air or steam injection under pressure to deeply scour and flush out oil and debris.
  • It specializes in high-temperature chemical dip tanks with industrial-strength solvents that break down years of oil residue and sludge.
  • Thermal treatments like professional oven heating or furnace burning remove even the most stubborn contaminant coatings from the delicate catalyst substrates via extreme temperatures.
  • Heavy-duty mechanical tumbling machines shake and beat the catalytic converter internals to break loose cell-clogging chunks of carbon that have solidified and baked on over hundreds of thousands of miles.

The typical cost for professional catalytic converter cleaning can range from $200 on the low end to over $500 depending on the specific cleaning methods required and whether the converter unit needs to be entirely cut out and removed to be serviced off the vehicle.

While decidedly pricier than DIY cleaning methods, for older high mileage vehicles in particular, having a professional service thoroughly deep clean the factory-equipped converter rather than purchasing a whole new replacement converter can provide substantial cost savings, often avoiding $1000 or more in new catalytic converter parts and installation labor.

Evaluating the Effectiveness of Catalytic Converter Cleaning

Once the cleaning process is complete, you’ll want to thoroughly assess its effectiveness before considering the job done. Here are some key checks to perform:

  • Road test the vehicle, paying attention to whether engine throttle response, acceleration power, and overall drivability are restored.
  • Listen for proper smooth exhaust tones without any remaining rattling or restriction sounds.
  • Compare fuel efficiency using the trip computer MPG gauge to see if gas mileage is now closer to EPA’s original ratings.
  • Monitor how quickly the engine reaches and maintains standard operating temperature after cleaning.
  • Carefully inspect for residual trouble codes or check engine lights related to insufficient converter efficiency or function. Re-check OBD readiness monitors to confirm all tests are running and passing.
  • Consider cleaning oxygen sensors using proper spray cleaners if performance seems to be still lacking after converter cleaning to rule out other exhaust issues.

A thorough cleaning often restores catalytic converter performance to satisfactory levels, substantially boosting MPG and power output while passing emissions tests. But repeat the cleaning process either DIY or via professional service if any significant symptoms persist.

Preventing Future Catalytic Converter Recontamination

Once a severely clogged catalytic converter has been sufficiently interior cleaned to restore proper exhaust flow and function, you’ll want to be extra diligent moving forward to avoid a repeat of rapid recontamination. Here are some converter care tips:

  • Properly repair even small engine oil leaks that could slowly foul the cleaned converter over time. Never tolerate any drips as they accumulate.
  • Avoid extended bouts of engine idling, which produces excess soot and carbon buildup on cylinder walls that will eventually reach the converter.
  • Use only top-tier gasoline brands containing effective, high-quality detergent additives to minimize carbon residue. Off-brand gasoline needs more detergency.
  • Let the engine fully warm up before aggressive acceleration to prevent raw fuel from entering the converter and misfires that could send unburnt fuel.
  • Consider preventive re-application of a light-duty cleaning additive every 60k miles.

Proper driving habits and regular maintenance keep your car’s high-performance catalytic converter clean. Follow the recommended intervals in your owner’s manual.

Conclusion on Catalytic Converter Cleaning

Thorough catalytic converter cleaning using proven methods can offer substantial cost savings over replacement in vehicles with high mileage but otherwise well-maintained engines. While not a fix-all solution, a clean converter optimized for proper air-fuel ratios helps lower emissions and maximize engine efficiency. Combine periodic preventive deep cleaning with diligent vehicle care for lasting performance. This guide gives you increased confidence to tackle converter cleaning safely and effectively. Please reach out with any questions!

Regarding homemade cleaners, I do not recommend these as they lack sufficient cleaning potency to handle severe carbon buildup. The key is using professional chemical formulations explicitly designed to cut through and dissolve away catalytic converter contaminants. Please let me know if you need any other conclusion topics or clarification covered!

Consumer Guidelines for Catalytic Converter Cleaning

Consult a Professional:

If you suspect an issue with your catalytic converter, it’s advisable to consult a qualified automotive technician. They can diagnose the problem accurately and recommend the appropriate course of action.

Follow Maintenance Schedules:

Adhering to your vehicle’s recommended maintenance schedule, including oil changes and tune-ups, can help prevent carbon buildup and extend the life of your catalytic converter.

Use Quality Fuel:

Opt for high-quality fuel that contains fewer impurities and additives, which can contribute to carbon deposits in the converter.

Address Engine Issues Promptly: 

If you notice changes in your vehicle’s performance or the “Check Engine” light comes on, don’t ignore it. Promptly address any engine issues to prevent contamination of the catalytic converter.

Avoid DIY Catalytic Converter Cleaning: 

Catalytic converter cleaning is a specialized task for professionals. Attempting to clean it yourself can lead to damage or incomplete cleaning, which may worsen the problem.

Consider Replacement: 

A severely damaged or clogged catalytic converter may require replacement rather than cleaning. Consult with your mechanic to determine the most cost-effective solution.

Check Emissions Regulations: 

Ensure that any cleaning or replacement of your catalytic converter complies with local emissions regulations to avoid legal issues and penalties.

Be Cautious of Additives: 

Be wary of products or additives claiming to clean catalytic converters. Some may not be effective or could harm your vehicle’s emissions system.

Get Multiple Quotes: 

If your catalytic converter requires replacement, consider obtaining quotes from multiple automotive repair shops to ensure you receive a fair price.

Maintain Records: 

Record all maintenance and repair work on your catalytic converter and exhaust system. This documentation can be valuable for warranty claims and future reference.

Frequently Asked Questions (FAQ) on Catalytic Converter Cleaning

What is a catalytic converter, and why is it important?

A catalytic converter is an essential component in a vehicle’s exhaust system that helps reduce harmful emissions by converting pollutants into less harmful gases. It plays a crucial role in reducing air pollution and meeting emissions regulations.

Why might I need to clean my catalytic converter?

Over time, catalytic converters can become clogged or contaminated with carbon deposits, oil, and other debris. This buildup can reduce their efficiency, resulting in poor vehicle performance, decreased fuel economy, and increased emissions.

How can I tell if my catalytic converter needs cleaning or replacement?

Common signs of a clogged or failing catalytic converter include:

  • Decreased acceleration.
  • Reduced fuel efficiency.
  • A sulfur-like odor from the exhaust.
  • The illumination of the “Check Engine” light on your dashboard.

If you experience any of these symptoms, it’s advisable to have your catalytic converter inspected.

Can I clean my catalytic converter myself?

Cleaning a catalytic converter can be complex and is not typically a DIY job. It’s best to consult a professional mechanic or automotive technician with the expertise and equipment to diagnose and address issues with your catalytic converter effectively.

What methods are used to clean a catalytic converter?

Professional mechanics may use various methods to clean a catalytic converter, including:

  • Chemical cleaning: Using special detergents or solvents to dissolve carbon deposits.
  • High-temperature cleaning: Employing heat to burn off accumulated contaminants.
  • Mechanical cleaning: Physically removing debris or blockages from the converter.

The specific method will depend on the extent of the contamination and the type of catalytic converter.

Is it possible to prevent catalytic converter issues?

To prolong the life of your catalytic converter, regularly maintain your vehicle, keep your engine in good condition, and use high-quality fuel. It will help prevent excessive carbon buildup and contamination of the converter.

I am Nicolas, an automobile engineer with over 5 years of experience in exhaust systems and catalytic converters. I am passionate about learning and understanding how things work, and I am always looking for new ways to improve the performance and efficiency of automotive exhaust systems.

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