How to Replace and Install Catalytic Converter? (Step By Step Guide)

Ever wondered how do vehicles minimize the pollution from their emissions?

Well, a device called catalytic converter converts the pollutants into eco-friendly or harmless gases. The major vehicular pollutants are carbon monoxide, hydrocarbons, and heat generated gases (nitrogen oxides).

A catalytic converter uses a catalyst in the form of platinum or palladium which converts these harmful gases into harmless gases.

Over a period, the catalytic converter loses its functionality and needs replacement. Therefore, let us know how to replace and install a catalytic converter for your vehicle.

What is a Catalytic Converter?

Catalytic Converter

A catalytic converter is a mechanical device inserted in the emission system of vehicles that use gas. It forms a series of reduction and oxidation (redox reaction) reactions which reduce the hazardous emissions from the vehicles.

French mechanical engineer Eugene Houdry was the pioneer in commercializing  the catalytic converter. He studied the effect of smog (smoke + fog) on the environment and was concerned about the impact of vehicular pollution on the environment.

The Catalytic Converter Has The Following Components:

  • A substrate or support for a catalyst which is made of ceramic or an alloy (iron-chromium-aluminum). The catalyst support is designed in the form of hexagonal rings to form a honeycomb structure. Honeycomb structure results in the larger surface area.
  • Oxides of Aluminum, titanium, and silicon are used as washcoat. These oxides or washcoats dispense the catalytic material over a large surface area.
  • Solid source of oxygen which does not decimate to heat. Most of the catalytic converters use an oxide of Cerium, a rare earth metal.
  • The final component of the converter is the catalyst. Precious metals such as Platinum, Palladium, Iridium, and Rhodium are commonly used as catalysts.
  • Palladium and rhodium are most commonly used as oxidation and reduction catalysts respectively. Platinum is a very active catalyst (for both reduction and oxidation) but is not applicable due to its high cost.

In summary, a honeycomb ceramic structure (alloy comb for high heat emissions) is coated with washcoat, oxygen dispenser, and catalyst which in turn is inserted into the exhaust system of the vehicle.

How Does a Catalytic Converter Work?

The catalytic converter works by two significant reactions:

  1. Reduction
  2. Oxidation
Reduction & Oxidation

The nitrogenous emissions are reduced (removal of oxygen) to nitrogen and oxygen. Nitric oxide (NO) and Nitrogen dioxide (NO2) are the major nitrogen compounds from fuel combustion which cause acid rains and smog.

On the other hand, an oxidative reaction will add oxygen to carbon monoxide (CO) and turn it into carbon dioxide (CO2). It also turns hydrocarbons into water (H2O) and Carbon dioxide.

In total, three reactions are happening in a catalytic converter, and hence it is called as three-way conversion and so the converter as a three-way catalytic converter.

Catalytic converters used in gasoline vehicles are three-way catalytic converters whereas those used in diesel vehicles are two-way converters.

Conversion of hydrocarbons is omitted in diesel engines because they do not emit much heat as gasoline engines do.

When to Replace a Catalytic Converter?

In general, catalytic converters have a very long lifespan. They can last up to 10 years. But there are sure signs which indicate that you have to replace them. These signs are:

  • Clogged exhaust
  • Overheating under the body of the vehicle
  • Significant reduction in the vehicle’s acceleration
  • A foul smell (rotten egg) from the exhaust

Some of these signs can happen due to other reasons such as engine coolant contamination or physical damage to the exhaust vent.

A technical guy will be able to diagnose appropriately and would suggest you to change the converter if needed.

How to Replace and Install Catalytic Converter?

Once you have decided to replace and install the catalytic converter, get all your gear that are necessary for the process. The tools required for this process are:

  • Wrenches
  • Ratchets
  • Ratchet extensions
  • Racket joints
  • Safety gloves and glasses
  • Jack and jack stands to elevate the vehicle above the ground
  • Sawzall or any other cutting tool for removing a welded converter
  • Penetrating oil to loosen up the bolts and nuts of the converter which usually get rusted

Steps In Removing The Catalytic Converter

The first step is to raise your vehicle so that you can move freely beneath the vehicle. Raise the vehicle to your comfort level and secure it with jack stands.

Do not forget to engage the hand-brake. If you are using a manual vehicle (geared), you can further secure the movement by putting the vehicle in gear.

Locate the Converter

Locate the  Catalytic Converter

Once the vehicle is raised, locate the catalytic converter. It is usually placed just before the exhaust pipe. Some vehicles may have multiple converters, and you have to locate the converter which you are intended to replace.

Remove the Sensor

Remove the Sensor

After finding the converter, remove the oxygen sensor from it. Some oxygen sensors are mounted over the converter while some are inside it.

Use the appropriate wrench or ratchet to remove the sensor. If there is no oxygen sensor, you can proceed to the next step.

Remove the Converter

Remove the Catalytic Converter

Now, it is time to remove the catalytic converter itself. Most converters are bolted to the exhaust. These bolts will usually get rusted over time. To remove the rusted bolts, use a penetrating oil.

Spray/pour the penetrating oil over the bolts and let them soak for few minutes.

The penetrating oil will make it easy to remove the rusted bolts by penetrating between the threads of the bolt (lubricating action). After lubricating the bolts, use assorted wrenches suitable for the bolt size and remove them carefully.

You may require extension joints or shoulders depending upon the location of the converter and the bolts on it.

For welded converters, use the Sawzall or any other similar to cut off the converter from the exhaust manifold.

Steps For Removing A Built-In Catalytic Converter

Certain vehicles have catalytic converters which are installed directly to the engine (cylinder heads). Locate the converter under the hood which is built into the engine.

The built-in catalytic converters are usually bolted (not welded) to the cylinder heads.

Locate the bolts and use penetrating oil if necessary. Use suitable assorted wrenches and remove the catalytic converter.

Steps For Installing The Catalytic Converter

After you have successfully removed the old catalytic converter, just follow the steps of removal in reverse mode.

  • 1
    It is advised to follow the instruction manual supplied with the converter. Position the gaskets (if present) in an appropriate position. These gaskets connect the converter to the exhaust unit or cylinder head (for built-in converters).
  • 2
    Tighten up the bolts with your hands first to hold the converter in position. Once in place, tighten up the bolts with assorted wrenches. Make sure there is no wobbling or shaking of the unit. A loose fit will affect the engine pick up as well the emission.
  • 3
    If your catalyst converter is a welded one, re-weld it again appropriately. The pipe ends of both converter and the exhaust must be sealed air-tight. If the pipe length is less, you can weld an additional pipe to fill the void.
  • 4
    Make sure to take all precautions during the welding procedure. Equip yourself with welding helmet with side shield, clothes that are fireproof, respirators, ear protection, gloves, and shoes.
  • 5
    After installing the converter, replace the oxygen sensor in its previous position and tighten up its bolts as well.

Re-check all the steps you have and make sure they are perfect.

Frequently Asked Questions (FAQs) 

How often should I replace the catalytic converter?

A catalytic converter will last long, and it does not require frequent replacements. If you are in doubt, take professional help.

What are the general precautions to be taken while replacing a catalytic converter?

Make sure your vehicle is secured over the jack stands. Always wear protective gear such as gloves, eye, and ear protection while doing the job. If you are unsure about the procedure, seek technical help.

Is it okay to replace one catalytic converter if the vehicle has multiple converters?

It is fine to replace one (damaged or non-functional) catalytic converter if your vehicle has multiple units.

Bolt's won't turn, what should I do?

Spray the penetrating oil and leave it for at least five minutes. It will lubricate them, and you will easily remove them.


The procedure of replacing and installing a catalytic converter varies from vehicle to vehicle. This guide is a general guide, and it is always good to follow the instruction manual.

The overall procedure is the same for all vehicles except for the type and location of the converter and the presence of the oxygen sensor.

If you are unsure about the procedure, get it done by a professional.

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