Catalytic converter failure 4.6is

[jontezan]

At the end of this season i have had a rattle from underneath the car. It has sounded like an loose heatshield around the exhaust. And only occured during idle. The car has been in the garage for a couple of weeks allready, but today i have norrowed down the problem. It is not a heatshield. There is a small dent in the driverside catalytic converter, and the cheramic inside is loose and causing the rattling sound. A new oem cat is out of the question because of the price. I have looked at this universal converter from magnatec as an exchange. Im planning on swapping both converters at the same time. In sweden we dont have californa rules on the yearly inspection. Input in this subject is appretiated. I have desent welding skills. https://www.summitracing.com/parts/mpe-51206


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[X53Jay4.8is]

If you go the aftermarket route then the key is to get a good catalytic converter because if not in few months or a year you'll be right back where you started from before. Can you get a used set from Ebay or the bone yard?

[jontezan]

Ofcourse there is. But kinda pricy too. Whats the difference on the cats between the 4.4 and 4.6? Theres plenty more salvaged 4.4 at the scrapyard = less than half the price. Dont see me as a cheapskate, but this was not planned in my fun budget for this winters maintenace


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[jontezan]

After checking realoem, it seems that 4.6 and 4.4 have the same exhaust manifolds. The cat for cyl 1-4 have matching numbers between 4.6 and 4.4. But on the driver side the numbers doesnt match?!? But in my opinion it got to be a match there to. I cant find any logical reason why the 4.6 would have a different type of cat on cyl 5-8


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[jontezan]

Today i purchased a used oem cat from a salvaged 4.6is. It was kind of pricy, but i can sell the old one for recycling and get 1/3 of the amount back


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[amancuso]

Originally Posted by jontezan

Today i purchased a used oem cat from a salvaged 4.6is. It was kind of pricy, but i can sell the old one for recycling and get 1/3 of the amount back


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Glad to hear you were able to sort it out.

[jontezan]

Originally Posted by amancuso

Glad to hear you were able to sort it out.

Thx i have not recieved the cat yet. But i think it will be a walk in the park to change it out. I changed the cupper nuts on the exhaust manifolds last winter, so they will come of easy


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[jcp240z]

The 4.6iS has unequal diameter headers. The drivers side cat tubing is 55mm in diameter while the passenger side is 50mm. The 55mm carries all the way to the silencer, it necks down at the silencer opening. The 4.4 is 50mm both sides.

I have never heard a definitive reason why, but assume it is to balance pressure drop due more bends and length on the drivers side.

[jontezan]

Originally Posted by jcp240z

The 4.6iS has unequal diameter headers. The drivers side cat tubing is 55mm in diameter while the passenger side is 50mm. The 55mm carries all to the silencer, it necks down at the silencer opening. The 4.4 is 50mm both sides.

I have never heard a definitive reason why, but assume it is to balance pressure drop due more bends and length on the drivers side.

Ok thx for answer. I didnt know that. But that makes sense. Good i ordered a spare from a 4.6. The spare is cut behind the rubbermount in the same lenght as a new replacement from the dealer would be. See if i weld it or if i buy the clamp that is intended for the job. Personally i like welded seams better than clamps


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[X53Jay4.8is]

Originally Posted by jontezan

Thx i have not recieved the cat yet. But i think it will be a walk in the park to change it out. I changed the cupper nuts on the exhaust manifolds last winter, so they will come of easy


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Personally I think this is the best way to go vs the aftermarket units. Keep us posted with the results when you receive it.