Oil leak: breather valve...?

[Jimmy6tring]

'01 S4, 16k mi, mostly stock.

I've got a slow leak that appears to be coming from the breather valve.  I've also heard this is a somewhat common problem.  Here's my questions:

The O-ring from ducati has to be ordered and will likely take a while but if I can find an oil resitant o-ring of the same dimensions is that a suitable alternative?

Is it likely that I'll have to replace the breather valve itself or is it just a bad seal, ie., replace O ring, tighten/re-seal and I'm okay?

Anybody know what size wrench I'll need to to get at it? I know I'll need to get one but I'm not sure the size.

Thanks as always!

[koko64]

As long as the breather body hasn't cracked.
Mine had an alloy washer. It was leaking as it was loose, but strangely the clamp on the hose was tight, so I don't know how it backed off. I added semi hardening  Permatex aircraft gasket sealant to the washer and mating surfaces and tightened it with a small C spanner. Hasn't leaked since.

[Howie]

Clean the breather and surrounding area well.  Then spray with an aerosol powder, like foot powder.  Go for a ride.  The oil stain will lead you to the leak.  Or. if there are a lot of miles on it, replacing may not be a bad idea.  I replaced mine at about 40K miles, it was weeping through the seam.  It was pretty nasty inside.

[koko64]

That foot powder trick is one of the best left field, diagnostic tools around. The first time I knew of it was on this forum.
Who'd have thought; foot powder!