What is a Catalytic Converter? The Catalytic Converter (commonly known as a Cat) is a device fitted in the exhaust system of your car that effectively reduces the harmful exhaust gases entering the atmosphere.
How does it work? The Cat works by filtering the exhaust gases through an internal honeycomb section known as a Monolith. The Monolith is either ceramic or metal and is coated with precious metals such as Platinum, Palladium and Rhodium that act as a filter for the harmful gases. Once these gases flow through the Monolith they are largely converted by a chemical reaction into non-harmful emissions such as water and carbon dioxide.
Why do I need to replace it? If the exhaust system is grounded or impacted in any way this can cause the ceramic monolith inside to collapse leading to failure of the unit.
If you drive through water when the Cat is at full working temperature the sudden cooling of the Cat can cause it to contract rapidly and therefore break up internally.
If your engine develops a misfire this can overheat and damage the Cat. A misfiring engine will send un-burnt fuel down your exhaust to collect in the Cat where it will ignite causing it to overheat.