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Learn how to replace a Catalytic Converter

How to Replace the Catalytic Converter

25 June 2015, 10:38

Most car owners will never need to replace their catalytic converter during the lifetime of their vehicle. They are built to last and are not exposed to the same levels of wear and tear as moving parts of the car. But a build-up of rust over time and significant knocks to the underside of the car could cause irreparable damage to your catalytic converter and mean that you would have to replace it completely. You could save yourself some serious cash by installing the new catalytic converter yourself.

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Here is a step by step guide of how to do so should you ever need to.


Make sure the car is parked on level ground and jack up all 4 wheels so that it is completely off the floor.


Make sure that the exhaust has had time to cool down. Don’t attempt to replace the catalytic converter straight after the car has been running.


Find the catalytic converter. It should not be difficult to locate, it will look like a box in the middle of the exhaust pipe system underneath the car.

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Inspect the converter to see whether it is welded or bolted to the car. If it has been welded in position then you may not be able to remove it yourself. If you have access to the correct tools and are confident removing the converter then you will be able to continue with the replacement yourself. If not, you will need to take your car to a garage to have a professional look at it.


Take the oxygen sensor off the main catalytic converter. Some models of car might have more than one oxygen sensor.

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Even if your converter is bolted rather than welded, it can still be difficult to remove. Rust can affect the bolts, making them extremely hard to remove. Penetrating oil could be your solution.


Every catalytic converter is slightly different, even though they all do the same job. This means that the installation process may differ from one converter to the next. If the new converter you have purchased comes with instructions, make sure that you read these through several times and follow them carefully.


New catalytic converters often come with small gaskets which fit inside the pipes which surround the converter and ensure that it sits tightly in place. If your converter comes with these then you will need to install them before you put in the converter itself.


There should be an arrow on your new catalytic converter to show you which way round it should be installed. You will also need to make sure that the right side is facing down when you put it in place.

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The next step is much easier if you borrow an extra pair of hands to help you. Holding the converter and working on it at the same time is no easy matter, so getting someone to hold it in place whilst you work on the bolts would be the best way of going about it.


Tighten the nuts as much as you can using just your fingers to start with. It will be easier to align all of the bolts in all of the bolt holes if you do not tighten them completely until all 4 are in place.


Most leaks in exhausts are due to loose bolts, so make sure that you tighten the nuts as much as you can.


Reposition the oxygen sensors and secure them in place. Double check that the wiring is correct, otherwise you could trigger dashboard warnings.


Once everything is back in place, it is extremely important to get your exhaust checked. Your car will need to pass an emissions test to check that it is safe for use on the road. The catalytic converter is an essential part of your car, and getting its installation wrong could have serious repercussions on your vehicle and the environment. If at any point during the installation you have any doubts or questions then you should take your car straight to a garage to have it looked at by a professional – this really is imperative!

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