Subaru DL Catalytic Converters Ultimate Guide

Subaru DL Catalytic Converters: The Subaru DL is a compact car produced from 1971 to 1989. Known for its affordability and reliability, the DL was equipped with various 4-cylinder engines. During its production, the Subaru DL models featured a single catalytic converter in their exhaust systems. This component was crucial in reducing harmful emissions and improving the car’s environmental impact. Despite its relatively simple design, the DL’s catalytic converter contributed to its compliance with emission regulations during its era.

Direct-fit replacement Subaru DL Catalytic Converters are available from aftermarket brands like Autozone catalytic converter, Bosal, Eastern Catalytic, and Walker. Proper inlet/outlet dimensions and flange style must match the original converters. Subaru DL Catalytic Converters sold in California must be CARB-compliant.

Specific Details on the Subaru DL Catalytic Converters

Common Signs For Bad or Clogged Subaru DL Catalytic Converters

  • Check engine light: Warning light for the engine. Checking the engine warning light is a valuable way to tell whether or not there is a problem with the emissions system in your vehicle. A professional mechanic must check out your car immediately if the “check engine” light turns on in your dashboard.
  • Reduced fuel economy: Your car’s fuel consumption efficiency may suffer if Subaru DL Catalytic Converters malfunctions since it cannot convert dangerous exhaust gases into less harmful gases at the same efficiency level.
  • Engine Misfires: If Subaru DL Catalytic Converters aren’t working properly, it could cause engine misfires. This is because the catalytic converter cannot reduce the quantity of carbon monoxide in the exhaust fumes.
  • Increased Emissions: A catalytic converter in your car that isn’t working properly may cause increased emissions. This is due to the inability of the catalytic converter to transform hazardous exhaust gases into gases that are less detrimental to the environment.
  • Excessive Exhaust Noise: Noise from the exhaust system that is excessive. A catalytic converter that is not working fine can create excessive noise from the exhaust system. This is due to the catalytic converter’s inability to significantly reduce the quantity of noise produced by the exhaust gases.
  • Dark Exhaust Smoke: An exhaust with a dark color is a symptom of a clogged catalytic converter, which can also generate this exhaust color. This is due to the inability of the catalytic converter to transform hazardous exhaust gases into gases that are less detrimental to the environment.

Troubleshooting Tips for Subaru DL Catalytic Converters:

  • Check for P0420/P0430 codes pointing to converter failure using an OBD2 scanner.
  • Listen for rattling noises from the exhaust, indicating internal damage.
  • Inspect oxygen sensor performance upstream and downstream of converters.
  • Look for reduced performance, increased fuel usage, and rotten egg smells.
  • Use Catalytic Cleaner for catalytic converting cleaning

Installation Tips:

  • Always replace the exhaust inlet/outlet gaskets when installing the new Subaru DL Catalytic Converters. High-temperature silicone sealant can also be used to seal connections.
  • The inlet/outlet pipe diameter is 2.5″. Ensure the replacement converters have the proper 2.5″ inlet and outlet ports.
  • When secured to the manifolds, use a torque wrench to tighten the converter mounting nuts/bolts to the proper spec of 22-27 ft-lbs.
  • Carefully detach and reattach the oxygen sensors from the original converters to the new ones in their same locations.
  • Clear any check engine codes with a scan tool after installing the new Subaru DL Catalytic Converters. This will reset fuel trim parameters and monitor operation.

Tips for Cleaning Subaru DL Catalytic Converters:

  • Use a catalytic converter cleaner. Products like Catalytic Converter Cleaners can help break down and remove contaminants and deposits inside the catalytic converter. Follow the directions on the product.
  • Flush the catalytic converter. You can do this by adding the catalytic converter cleaner to your gas tank when filling up and then driving the car for 30-60 minutes on the highway. The high speeds and engine heat will help circulate the cleaner through the catalytic converter to remove deposits.
  • Use a shop vac to vacuum out loose debris. Disconnect the oxygen sensor and carefully insert the vacuum hose into the catalytic converter inlet. Be careful not to damage the honeycomb structure inside.
  • You may need to remove the catalytic converter and soak it in a solvent-based or acid-based cleaner for heavy carbon deposits. Make sure to thoroughly rinse and dry it before reinstalling.
  • Avoid using engine degreasers or harsh chemicals that could damage the catalyst material inside the converter. Stick to products specifically made for catalytic converter cleaning.
  • Be gentle in your cleaning methods to avoid damaging the converter. Over-cleaning or using too much pressure can harm the internal structure.
  • Consider having a professional mechanic do the cleaning if you’re uncomfortable with the process. They’ll have the proper tools and skills.

Some Tips For Properly Washing Subaru DL Catalytic Converters

  • Use a degreaser or catalytic converter cleaner. Spray it directly onto the exterior casing of the Catalytic Converters and let it soak for 5-10 minutes. This will help break down oil, grease, and carbon deposits. Avoid getting cleaner inside the converter.
  • Rinse the converter thoroughly with a garden hose or pressure washer. The high-pressure water will help blast away loosened contaminants.
  • Use a soft brush or rag to scrub the converter’s outside for stubborn deposits. Avoid abrasive pads or brushes that could damage the metal casing.
  • Ensure you thoroughly flush out any catalytic converter cleaner you use with plenty of water. Leftover chemical residue can damage the catalyst over time.
  • Dry the Subaru DL Catalytic Converters fully after washing, using compressed air if available. Moisture left inside can also degrade the catalyst. Let the converter idle for 10-15 minutes to help evaporate any moisture.
  • Avoid using harsh chemicals like engine degreasers directly on the converter, as they can wash away the catalyst material and degrade performance over time.
  • Do not attempt to wash inside the converter or scrape at the honeycomb – this will destroy it. Only clean the outer casing.
  • Consider having a professional detail shop wash the catalytic converter if you don’t have the proper tools. They can properly clean it without damage.

The key is to be gentle and use only Catalytic Converter-approved cleaners. Thorough rinsing is important. Avoid excess moisture inside the converter.

Life Of Subaru DL Catalytic Converters

  • Under normal driving conditions, the OEM Subaru DL Catalytic Converters can average 120,000-150,000 miles.
  • The converters have an 8-year/80,000-mile federal emissions warranty. California emissions models have a 15-year/150,000-mile warranty.
  • Driving style has a big impact. Many short trips and cold starts can foul the converters faster than longer highway driving.
  • Poor engine maintenance, like oil leaks, bad spark plugs, or issues causing misfires, will degrade the converters quickly.
  • Contaminants like oil, coolant, or fuel getting into the exhaust can coat and damage the converter’s internals.
  • The upstream converter near the engine tends to fail sooner due to more heat cycling. The downstream one often lasts longer.
  • The efficiency declines if the Check Engine light comes on for a catalytic converter code. Replacement is recommended.
  • Periodic visual inspections of the converters can help spot potential issues early. Signs include blocked flow, rattling, and visible damage.
  • Aftermarket replacement converters typically have a shorter 50,000-80,000-mile lifespan. OEM parts tend to last longer.

How To Replace Subaru DL Catalytic Converters


It uses multiple catalytic converters, one on each exhaust manifold bank. The new converters must be bolted into the original mounting positions for proper exhaust flow.

Exhaust Seals:

When installing the Subaru DL Catalytic Converters, use new gaskets to seal the inlet and outlet flanges. Apply high-temperature silicone sealant as well to prevent leaks.

Oxygen Sensors:

Carefully detach and reattach the oxygen sensors from the old converters to the new ones. Position the upstream and downstream sensors properly.

Inspect Other Components:

Inspect the exhaust manifolds, mounts, and pipes when replacing the Subaru DL Catalytic Converters. Look for any leaks or damage that needs addressing.

Post-Installation Check:

After installing the new Subaru DL Catalytic Converters, clear any codes and road-test the vehicle. Verify the catalyst efficiency monitors are set to ready and that no check engine lights return.

FAQs about Subaru DL Catalytic Converter

What is a Catalytic Converter, and how does it work in Subaru DL?

A Catalytic Converter is an emission control device that reduces harmful pollutants from your vehicle’s exhaust gases. It uses a catalyst to convert carbon monoxide, hydrocarbons, and nitrogen oxides into less harmful substances like carbon dioxide and water.

How long does a Subaru DL Catalytic Converter typically last?

The lifespan of a Subaru DL Catalytic Converter can vary depending on driving conditions. Still, they often last between 70,000 – 100,000 miles. Proper maintenance and avoiding issues like clogged converters can extend their life.

What are the symptoms of a clogged Subaru DL Catalytic Converter?

Symptoms of a clogged catalytic converter in a Subaru DL include reduced engine performance, poor fuel efficiency, and the illumination of the “Check Engine” light. It may also produce rattling or metallic noises.

Can a clogged Subaru DL Catalytic Converter be cleaned, or must it be replaced?

Generally, a severely clogged catalytic converter needs replacement. However, you can use a catalytic converter cleaner for minor clogs as a temporary solution. For a long-term fix, replacing it is recommended.

What is the cost of a replacement Subaru DL Catalytic Converter?

The cost of a replacement catalytic converter can vary depending on the model, brand, and location. On average, you can expect to pay between $200 to $1,200 for the part, excluding labor costs.

Can I sell my old Subaru DL Catalytic Converter as scrap, and how much is it worth?

Yes, you can sell your old catalytic converter as scrap. The scrap value depends on the type of metals used and current market prices. Prices can range from $50 to $250 or more.

What are the best practices for maintaining a Subaru DL Catalytic Converter?

To maintain your catalytic converter, use high-quality fuel, fix engine issues promptly, and ensure proper vehicle maintenance. Regularly inspect and clean your converter to prevent clogs.

Are aftermarket catalytic converters a good option for Subaru DL owners?

Aftermarket catalytic converters can be a cost-effective choice. However, ensure that the aftermarket converter meets emission standards and is compatible with your vehicle’s make and model.

How can I prevent damage to my Subaru DL Catalytic Converter?

To prevent damage, avoid driving with a misfiring engine, fix exhaust leaks promptly, and refrain from using leaded fuel. Also, drive cautiously to avoid hitting obstacles that could damage the converter.

Is driving a Subaru DL with a removed or malfunctioning catalytic converter legal? 

Driving without a functional catalytic converter can violate emissions regulations in many areas. It’s essential to check local laws and ensure your vehicle complies with emissions standards.

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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