The last leak on my alfa was coming from the distributor seal - I wasn't 100% sure so decided to take it off and check, took in all 10 minutes to confirm, plus 10 minutes to put it back on and 1,50€ for the O ring. No more leaks there!
Very easy to do.
1. remove distributor cap and move it out of the way (splash guard too if this is fitted)
2. Note in which direction the rotor points to (drawing or photo helps, as you WILL forget!)
3. Remove 10 mm mounting bolt as in photo 1 (thanks to Vintre on alfabb for this one)
4. Pull out dizzy and look at the leaking oil as in photo 2
5. Stuff a rag down the hole and spray all the nasty oil that has been leaking with brake cleaner so it looks like photo 3
6. throw away old O-ring which has now become hard and useless (like mine!)
7. clean outside of dizzy a little
like photo 4
8. Put in 1,50€ O ring (to be seen in photo 3)
9. replace dizzy REMEMBERING where the rotor was pointing to (....you see, you already forgot...!!)
10. Tighten 10mm bolt whilst pushing down on dizzy (as new O ring is fatter and you do not want to stress the 10mm stud!)
11. refit dizzy cap.
NOTE: the S4 dizzy does not have an oil seal on the shaft itself, just on the block and the distributor clamps down on this causing the necessary seal
That was the last engine leak that was annoying me(for now)!