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Exhaust Leak At Catalytic Convertor – Buy New or Weld?


Exhaust leak? Is it the Catalytic Convertor?

MVS Contributor Kahl has an exhaust leak at the catalytic convertor on his 2000 Volvo XC70. Then he fixed it by being a man and DIY welding it, instead of taking the easy but expensive route of buying a new cat.

While under the car with it running I heard the ringing of a exhaust leak coming from the cat. I cut the protective shield shield so I could pull it out of the way. There was a crack/hole in the center where the rivet is seated. Ground off rust and welded in a sheet of stock to seal off the leak. Beats buying a new cat. It is so nice to have a neighbor with a lift and welder.

MVS member 57gretsch too had an exhaust leak, and just saved himself huge money over buying a new cat:

Just did the same thing on Monday. Also welded up the joint closest to the manifold. I was told that I needed a new cat when I took the car in for a safety. After pricing them out I decided to have a look myself. Won’t be going back to that station anytime soon for opinions or work.

MVS Moderator JDS60R adds good info:

When I lived in MA we would get 2 years from a steel patch and an almost permanent fix from stainless. I know Volvo used 400 series stainless for some of the cats but that rust shouldn’t be that bad on 400.

If you need a cat you can run a magnaflow 51356 if it needs a center bung or a 51206 if you don’t. If its a 98 or similar you can run a 99065HM Either way you will need a 45 degree bend to remake the turn between the flex joint and the new cat. (Many volvo cats are 20 inches long while most aftermarket cats are 11 to 15 in long).

Part numbers above are for federal emissions . If you need CA or NY call Magnaflow and they will tell you equivalent.

Some require a bung in the 45 degree section (98 and similar) so pick up a bung while shopping. I tig in with 309L rod . expect to pay $30 for the 45 bend, $100 for a magnaflow cat and $10 for a bung.

Magnaflow also has the entire downpipe but its $500


Exhaust leak fixed
Tacked sheet first then filled in
Stock sheet metal
Heat shield cut free
Crack at rivet


2000 V70 XC crack in cat

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