just thought I'd share this with you:
some time ago my car (2.0 16v) developed an oil leak from the flywheel housing. When I checked this forum I came cross some posts on crankshaft seal problems, and how renewing the seal rarely helped. Well, I went ahead and pulled the gearbox (what a nightmare, mainly thanks to the previous garage stripping several engine mounting bolts and putting them back in with a bit of coppagrease; my car now has the largest engine mounting bolts in the world), clutch and flywheel, and found a big oily mess on the side of the engine. Cleaned it all up, and put in the new seal with lots of gasket sealant. At that point it was time to get a few hours of sleep.
Coming back the next morning, I was greeted by the sight of oil dripping from the side of the engine! eek! It turned out that the oil was leaking from the bung sealing off the hole where the balance shaft lives. I managed to pry this plug out, cleaned it all up, and put it back with a nice fat blob of sealant. Guess what? No more oil leaks from the bellhousing!
It's pretty obvious to me how these horror stories about bad crankshaft oil seals came into the world. A garage changing the oil seal would probably do it in one day, and in the mass of oily crud in the bellhousing it's easy to miss the oil welling up from the balance shaft bore. So the crankshaft seal would have gotten changed, without it being the source of the problem. So next time somebody has an oil leak repaired, tell the garage to check/change the balance shaft plugs.
So there you are, another fairy-tale about unreliable alfa angines shot to bits! We'll get there in the end...