How to Replace a Catalytic Converter With a Straight Pipe

by Thomas West
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under truck image by Patricia Mesanko from

Catalytic converters have been installed in cars and light trucks since the mid-1970s. The catalytic converter cleans the vehicle's exhaust gases before they are expelled from the exhaust pipe. When a catalytic converter starts to fail, your vehicle may not only run poorly, but it may not pass an emissions test due to excessive pollutants coming from the exhaust. Before replacing your expensive catalytic converter, make sure it is the culprit by replacing it temporarily with a straight pipe, sometimes called a test pipe. If your car runs properly with the test pipe in place, your catalytic converter will need to be replaced soon.

Step 1

Park the vehicle on a level surface and raise it with a hydraulic jack. Place jack stands under each corner of the vehicle's frame. Lower the hydraulic jack until the vehicle is fully supported by the jack stands.

Step 2

Allow the exhaust system to cool if the vehicle has been driven recently, as the catalytic converter can be extremely hot.

Step 3

Crawl under the vehicle and spray penetrating fluid onto the catalytic converter mounting bolts. Allow the fluid to work in for at least fifteen minutes.

Step 4

Loosen the mounting bolts on each end of the catalytic converter with an adjustable wrench in a counterclockwise direction. Remove the bolts and place them aside. Lower the catalytic converter carefully to the ground. Retain the catalytic converter for possible installation in the future.

Step 5

Place a test pipe (available at auto parts stores) into the exhaust system in the void left by the catalytic converter. Twist the pipe around by hand until the mounting holes in the flanges on the test pipe and the adjoining exhaust pipes line up.

Step 6

Place the original mounting bolts into the holes in the flanges and tighten with an adjustable wrench in a clockwise direction.

Step 7

Raise the vehicle with the hydraulic jack and remove the jack stands. Lower the hydraulic jack until vehicle is resting on the ground. Remove the hydraulic jack.

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