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Got any tips on installing new cats?

Fu Manchu

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So my cats are stuffed. They both sound like they are filled with nuts and bolts.

Started with a power saw like vibration sound. Then progressed to squeaky and rattley sound.

As luck would have it, two come up on gumtree with 80000ks on them.

I am also hoping changing these resolves the MAF code being thrown which I now put down to the greatest hidden vacuum leak in human history or partially blocked cats that have now fallen apart.

One has a bit of tig in it from the bracket that holds the insulation on the outside. I might get that off with some pliers.

Visual inspection of the cats looks great from what can seen down the pipe. The O2 sensors had good colour. Test ok as well.

• One pipe has a slight flat spot on the flange that couples to the exhaust manifold, do I need to sort it?

• Do I need a gasket there or is it coupled to the exhaust manifold as metal on metal, no sealant or gasket? (I understand silicones and cats don’t go well)

• Connecting the rear flange, Should I use any silicone with a metal gasket?
• Do I need a specific gasket?
• Recommendations on a brand to use?

Lastly:

• Any tips on getting the two nuts off the manifold flange? In particular the drivers side? (Also getting them back together?)
 

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99notout

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Mate, I just had aftermarket cheapies welded in. Solved the problem and has been fine that last couple of years now .... Fingers crossed!
 

BowTie

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Manifold nuts. Wd a couple of times the night before.

I use two long half inch socket extensions with the socket end being undercut to allow the socket to pivot on slighty. With a breaker bar from underneath.
 

Fu Manchu

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Did the job. There is no gasket between the exhaust header and cat section of exhaust.

I used some high temp silicone on the rear gasket. Used new bolts. New nuts on the header.

Amazing results.
 
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