I read somewhere you need to break in a new catalytic converter. To that end:

  • Is this accurate?
  • What is the purpose of breaking one in?
  • How do you break it in?

1 Answer 1


This website seems to answer all of the questions you have asked above.


The website discusses proper procedures to make sure that the catalytic converter is broken in correctly.

At the bottom of the article there are steps to break in the catalytic converter.

There are also some other links on the left of the article that involves catalytic converters.

The main information for the website is presented below here. I give all credit to the website with their information below and on their website.

A replacement catalytic converter needs to undergo a proper “break-in” procedure to ensure that it will con­tinue to work the way it is supposed to and deliver the required emissions reliability and long service life. If the converter is not warmed-up properly (broken-in), the substrate inside could be adversely affected and eventually cause the converter to fail down the road.

A proper break-in period is required for a correct installation:

The problem typically occurs when a shop installs the converter and immediately returns the vehicle to the customer without warming up (breaking-in) the cat.

The customer drives away and runs the car for a long distance or lets the vehicle idle for an extended period of time. Under these conditions, the matting, which is intended to secure the substrate will not expand properly and hold it in place.

Converter matting is made from a mineral called vermicu­lite, which is held together by a fiber mat and an organic binder. This matting is wrapped around the converter’s ceramic brick (See Figure 1).

The matting is installed in the converter in an unexpanded state (See Figure 2). During the first heat up, the fiber mat and binder burn off and the mat­ting actually gets looser before it expands to fill the converter cavity and hold the ceramic brick in place (See Figure 3). If that warm up is not done properly, the brick can come loose and get damaged. That rattle you might hear inside the converter shell is a sure telltale for this problem.

Warm up that cat first.

The best way to avoid this service issue and potential war­ranty problems is to include the warm-up period as a key part of your overall converter installation procedure. This heating cycle will allow for correct matting expansion.

Here are suggested steps for a proper break-in or warm-up:

Start engine but do not touch the accelerator pedal. Idle the engine and allow it to warm up slowly. After 5 minutes, increase the engine speed to 2500 RPM. Hold at 2500 RPM for 2 minutes. Allow engine to cool down. Road test vehicle to confirm correct installation.

  • Thank you. I have a deep passion for the automotive world. I liked the question a lot. Most people just think of breaking in an engine. Kudos to you sir.
    – mr_tuner
    Mar 13, 2016 at 1:52
  • Be sure to stop by The Pitstop, our chat room. Mar 13, 2016 at 3:38
  • Great answer indeed, but it would be great if you added a short version of the break in procedure to the answer as well. Nothing is more frustrating when you are looking up a problem online, find someone mentioning it with a link to the solution and when you click it you find that it's dead. Mar 14, 2016 at 9:48
  • @IhavenoideawhatI'mdoing The information from the website is included in the answer. It starts at the 6th sentence to the end of the answer.
    – mr_tuner
    Mar 15, 2016 at 23:01
  • @mr_tuner - I think he was talking about a TL DR cut at the beginning of your answer. You have it at the end, but it's okay. Jun 22, 2016 at 22:42

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