Leak in exhaust flange to catalytic converter

My car has failed its WOF due to a leak in the flange to the catalytic converter. The muffler shop recommends removing the whole cat' and lengths of pipe around it and substituting in a resonator box. Would removig the cat', an emissions control device give me any issues in the future with passing WOFs! Obviously we do not have emissions testing in NZ, but I thought tampering an emissions device is a WOF fail. The shop advises that it won't be a problem however. Also could there be any other issues, like with the car's computer!

The shop says putting in a resonator would cost $250, but if I really wanted I could put in a new high-flow cat' at a cost of $500 all up. I do not mind spending extra, but doing do for no reason would be silly.

Car is a 1999 Mitsubishi Legnum VR-4 with a factory exhaust. A factory standard car, with 123,000km on the clock. Car is an auto and black in colour, LOL.

just find another secoundhand cat from where ever be plenty mitsubishis abouts for parts.

Why can't the leak just be fixed!

I'm thinking new gasket/flange.

The muffler shop says they can fix the leak, but that it would take quite a bit of time in labor, so rather than fluffing about with that I should cut the whole cat out. Replacing the cat will improve performance and fuel economy too they say, which sounds like a good idea in theory anyway.

A new flange gasket must be all of $10 and 1 hour of labour take the car somewhere else you are being ripped I replaced the cat on my diesel Pug with a straight piece of pipe $50 at Midas, Taradale

Would replacing with a straight pipe effect the sound. I am not wanting the car to sound louder!

Generally won't affect sound, and realistically, will make very very little difference to Performance & economy (Early CAT's did but modern ones hinder to such a small extent you'd only really see a gain on a dyno and it would be minimal at best)

There has been talk for a while of the Govt bringing in emission laws so that CAT's can't be removed etc, but it has always just been talk and I haven't heard anything definitive.

If you do get it cut out, Ask to keep the CAT in case that does come in so you can refit it - they are also worth a bit of money, so the exhaust shop would be looking to make extra profit out of you by recommending you to get the CAT taken out as they will expect you to not want it and then they can onsell it to scrap metal (Usually around $50-$100 worth, has platinum inside them)

What about safety when handling cat's! Don't they contain carcinogens and such! If so I would prefer to let the shop dispose of it, rather than have it hanging about in my garage.

They're worth good money scrapped (apparently) - palladium is expensive stuff.

it be definetlyloads louder with a straight pipe and the oxigen sensore needs to be there dont know about mitsis but some cars will even need a remap of the ecu when you remove the cat., plus it is a fail of a wof if its removed. you no longer are allowed to remove them. in your case it should fail the wof as it clearly had acat on the wof sheet.

the wof rule say from this and this date on your no longer allowed to remove the cat if it had one. Dont know how they proof it was removed before the date this law came , but in your case it be easy to proof that it had acat as it faild on a crack with cat as wof fail. the below said you canbut i did read the wof rule once said your no longer allowed to remove it and i was thinking how are they gona proof it was not removed prior to that date where you where not alowed to remove it no more.

Reasons for rejection;
A vehicle (other than group L vehicle or a class MA or MC motorsport vehicle with a valid motorsport authority card) that was first registered in New Zealand on or after 1 May 2010 and manufactured from 1 January 1990 has a catalytic converter removed where there is evidence that one was originally fitted, and there is no written evidence issued by a TSDA that the vehicle passed a prescribed metered emissions test in this condition

If your vehicle was first registered in NZ prior to 1 May 2010, it is exempt from this rule and provided the exhaust system meets the objective noise level test and does not leak, then it will pass a Warrant of Fitness inspection.

I can understand the reasons for removing the catalytic converter (normally high cost) although it does allow the vehicle to produce higher tail pipe emissions which is not desirable for the environment.

Any car fitted with a catalytic convertor will also have what is called an oxygen sensor fitted into the exhaust system just forward of the converter.

It is very important this sensor is left in place as it is connected to the engine management system and to the dash engine warning light.

If it is disconnected the dash warning light will stay on which is a definite WoF reject.

The oxygen sensor is there to protect the convertor by monitoring the air/fuel mixture in the exhaust system and will continue to operate regardless of whether the catalytic convertor is fitted or not.

It would definitely pay to check with your warranty insurance under-writer and ask whether this change has any affect on your policy.

They may also mention the oxygen sensor issue.

Good info thanks. Have had this car many years. First registered in NZ by me in 2005. No warranty on it.