Warranty Information

Catalytic converters should not fail under normal operating conditions. If it has, the most likely cause is a problem with the car. The following faults are not covered under theterms of our guarantee.

Road/Impact Damage

Impact damage is caused to the catalyst when it hits, or is struck by hard objects. This can cause the monolith to fracture and the pieces to rattle around inside the unit. Possible causes are a hard object striking the converter, hitting speed bumps and offroad

driving. Impact damage can usually be seen with the naked eye on the housing of the unit.

Plugged or Contaminated Monolith

This is when the monolith becomes coated and blocked with soot, preventing it from converting the gases that pass through it. This can be caused by the car running rich, using the incorrect fuel or unsuitable fuel additives and oil or antifreeze entering the

exhaust. Excessive levels of hydrocarbons (neat fuel) entering the exhaust can also contaminate the monolith and prevent it working. Always ensure that the vehicle is running at no higher than 55PPM HC before fitting a new catalyst*.

Melted or Broken Monolith

Monoliths can be broken in a variety of ways, the most common being impact damage (see section above). It can also be broken when it suffers a sudden drop in temperature (e.g. driving through a ford) as the steel shell contracts faster than the

ceramic monolith as it cools and crushes it. The monolith can be melted when unburned fuel is injected into the catalyst. Causes of this are tow or bump starting, or the car’s engine not firing properly on starting. More information on the causes of melting

monoliths can be found below.

Overheating

There are many problems that can cause a catalyst to overheat or fail. The most common of these is when unburned fuel enters the catalyst. This fuel ignites when it reaches the catalyst because of the high operating temperatures, causing the catalyst

to superheat and melt down. Some causes of this are faulty spark plugs and leads, which cause the engine to misfire and a badly timed distributor.

Oxygen /Lambda Sensor

The oxygen (lambda) sensor collects and sends information to the ECU (Electronic Control Unit). This is used to control the air/fuel mix. If the oxygen sensor is faulty, the air/fuel mixture will not be corrected. In the case of it running rich excess fuel will enter

the catalyst, causing it to superheat and melt down. It is advised that a new oxygen sensor is fitted every time a catalyst is replaced.

Fuel Injection Systems

A catalyst can be damaged if a fuel injector is leaking internally or dribbling fuel into the engine. The excess fuel will then enter the exhaust system and superheat the catalyst, causing the monolith to melt down.

Map Sensors

Map sensors inform the ECU of the load on the engine and the amount of air entering it. If this sensor fails it causes a rich condition in the engine, which can superheat the catalyst and cause it to fail.

Carburettor Systems

A worn or defective carburettor can cause a catalyst to overheat. Problems such as improper float or air/fuel mix adjustments and worn metering rods can damage the catalyst. The choke system also needs to be operating properly so the right level of

fuel enters the system. If too much fuel enters the system the catalyst will overheat and eventually fail.

Canister Purge Valve Control

This vacuum operated valve vents fuel vapour from the carburettor bowl to the charcoal canister. If the vacuum is breached, the charcoal canister will flood and the air/fuel mixture will become very rich. This excess fuel will enter the catalyst and the monolith

will melt down.

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