Header to cat connection

[Bushum]

When I was installing my new mid-pipe I attempted to take the bolts off the flange from the cat to the header but before I could, the cat slid off. I slid it back on and finished the install but I was wondering if this is normal. I was thinking that this may be what causes the exhaust leak sound at cold start. When the exhaust heats up it expands and makes a tighter seal. So is this something I need to fix or is it how the exhaust goes together?

[W Cole]

The X pipe fell apart from the headers without taking the bolts out? Definitely not normal. Replace the seals and re-tighten. Should be ok then.

[M3an V8]

I suppose its not normal for the cat to slide right off without undoing the bolts, however, the flange on the header side it not really stationary(ie: welded on). When I installed my Remus h-pipe, I decided not to drop the exhaust, when I was halfway through cutting with the electric saw, the driver side vibrated off the header. Well I finished the install, shoved everything back, but I did ended up replacing the "donut" seals a month later.

[Bushum]

Originally Posted by M3an V8

I suppose its not normal for the cat to slide right off without undoing the bolts, however, the flange on the header side it not really stationary(ie: welded on). When I installed my Remus h-pipe, I decided not to drop the exhaust, when I was halfway through cutting with the electric saw, the driver side vibrated off the header. Well I finished the install, shoved everything back, but I did ended up replacing the "donut" seals a month later.

That's exactly how it happened to me. The flanges stayed bolted together but slid off of the header. It was probably from the vibrations of the reciprocating saw. Is the donut seal between the two flanges? Did you replace them out of necessity or just because you wanted to?

[M3an V8]

Originally Posted by Bushum

That's exactly how it happened to me. The flanges stayed bolted together but slid off of the header. It was probably from the vibrations of the reciprocating saw. Is the donut seal between the two flanges? Did you replace them out of necessity or just because you wanted to?

I replaced them cause I got bored, but honestly there were no signs of audible or visual (black soot etc...) leak.

Yes the donut seal is between the header and cat flange.

[W Cole]

Originally Posted by Bushum

That's exactly how it happened to me. The flanges stayed bolted together but slid off of the header. It was probably from the vibrations of the reciprocating saw. Is the donut seal between the two flanges? Did you replace them out of necessity or just because you wanted to?

Cheap insurance to replace it every time you take off the x pipe. Especially if it fell off like yours.

I replaced mine the first time I swapped the x pipe but was too lazy to the second.