Exhaust Water Leak @ Section 2 to Muffler Junction

[E46_M3_ZCP]

I've been having this "issue" with what I would call a condensation water leak at the two pipe junction where the factory section 2 transitions into my Dinan muffler.

I wanted to know if this is a common issue and if there are any known fixes that I'm unaware of.

The small drip condensation water leak is noticed when the car is idling and a wet spot can be noticed on the pavement directly below the section 2 to muffler junction point.

I've pinpointed the source of the leak to be coming from the inner pipe which joins two flared exhaust pipe ends using a donut shaped non-compression style sealing gasket.

This donut style gasket seems to me to be a ridiculous gasket because unlike the other pipe which slides into a good couple inches into the other and has more of a compression style gasket that actually has a chance of sealing.

Is this an issue specific to the Dinan muffler or does it occur even with the factory or other aftermarket mufflers?

[jbfrancis3]

It occurs with the factory and other style mufflers. The steel ring “gasket” needs to be perfectly clean to make a good seal and even then I couldn’t tell you if you’d achieve watertightness.

If it really bugs you, you could clean up the two flares and the steel ring with steel wool or scotchbrite pad. Again don’t be surprised if you still get a drop or two. Resist cranking down on the bolts as you risk breaking the OEM section flange which isn’t replaceable (due to the flare), unless you go with an inferior 2 piece aftermarket flange.

[Casa de Mesa]

Funny, when under my car over the weekend, I noticed the same thing but where section 1 and 2 meet. It's a flat gasket there as opposed to the o-ring style.

FWIW.

[Cubieman]

Resist cranking down on the bolts as you risk breaking the OEM section flange which isn’t replaceable (due to the flare), unless you go with an inferior 2 piece aftermarket flange.

Good tip. I have an unfortunate tendency to over tighten and bent the flange on my SCZA, figured I'd have someone weld a two piece flange back on if it became and issue.

[E46_M3_ZCP]

A water leak at the section 1 to 2 interface is most likely due to failed flat gaskets as I've never had a leak at that point.

I torqued the fasteners at the section 2 to 3 down to the recommended 15 N-m but maybe even that is too much for the clamps as they still tend to bend slighly with that recommended torque value.

I'm trying to understand why BMW decided on this inferior sealing style of joint with flared ends at the section 2 to 3 interface as opposed to just repeating the same joining design as used at the section 1 to 2 interface.

[CrisSilberGrau]

Redid my sec2 to muffler hardware in SS since I hated the rust accumulated. Had the same issue, however it was more due to Supersprint sec 2 not lining up to scza properly on that specific side. Definitely used more than 15nm force though.

[E46_M3_ZCP]

Yours don't look that bad. I'm thinking of applying a little bit of this Permatex Muffler & Tailpipe sealant. Anyone have any experience using something like this?