[WKvernich]

00 Mustang V6 , header leak fix - YouTube

00 Mustang V6 , header leak fix - YouTube

Is this the part you are talking about? Mine is a Gt but I'm assuming it looks like this?

[jeep45238]

Yes, but the flange doesn't break off (mine is a GT as well). Just the mid pipe connection at that point, but on the driver's side.

It is a VERY common deal on these cars when people put in mid pipes - do a search for exhaust leaks in this forum, you'll see that most of them are on the driver's side, and all have the same problem.

To give you an idea why you need antisieze - most of the force you exert on a fastener is spent overcoming friction - like, 75% or something like that. That is the reason why ARP suggest moly for their fasteners when torquing to spec, and a vast amount of manufacturers require dipping their head bolts in oil, and then torqing to spec.

My 450 ft. lb. impact didn't have enough oomph to do the job. I used my 18" 1/2 drive breaker bar, 1/4-1/2 turn at a time, until I crushed the steel of the mid pipe well enough to seal on the dome of the collector.

[WKvernich]

Any reason I'm only hearing this while driving above 3k rpm? The best way to describe it would be that it's like a rattling noise. I can also hear it on start up, sounds like air escaping from it. Anyway I'll probably have my buddy fix it in about a week or 2. Here's a picture.

[jeep45238]

More RPM's = more exhaust volume = louder at leaks. Small leaks tend to do a slight whistle noise (best description my sleep deprived ass can come up with right now).