'05 MCS..... Can I simply gut the pre-cat??
 

Exhaust started making an intermittent loud noise Monday and last night something popped when I hit the gas then it sounded like an open header....sure enough once I got the car up on stands the weld area separated on the lower side of the pre-cat. This is a stock car, I'm not looking to add expensive parts I just want the exhaust working again. I can weld the stock header back together but am wondering if I should gut the pre-cat first? I know the pre-cat can be removed without the check engine light coming on but is there any other downside to doing this? If I weld it back together as is with the weld being right next to the ceramic catalyst will the heat from the welding damage the pre-cat?

Thanks in advance....

The car will run fine and not have a check engine light if the precat is gone as it doesn't effect the oxygen sensors.

Thanks, I'm gonna gut the pre-cat and weld it back up like it is and when I have more time I'll take it back out and replace the pre-cat with a section of stainless tubing. This way I'm back on the road soon as I have two trips to make in the next month or two. I'll be in Atlanta in the next couple of months in the car so I'll stop by and see your shop and pick up some items I need.

The welding repair can be done without gutting the pre-cat. The trick is to weld to the external casing of the pre-cat which make the repaired header stronger than new. I would not bother with SS tubing. SS can be welded with MIG.

Well, I have already gutted the pre-cat so that is moot and I realized, as you stated, that welding the outer casing to the original weld would be much stronger so that is what I plan to do as soon as my buddy gets a new bottle of gas for his MIG.