All depends on which bit of the engine is oily....most of em that age are cruddy all over!
From the above, and depending on how high up the engine the leak starts, check the following:
1) Oil breather 'stack' - it has for 8mm nuts, check they are tight (but not TOO tight, its plastic!). There is a large, easily replaceable 'O' ring at its seat, if you need to change it (JK do em)
2) Front crankshaft oil seal (behind the big main pully) - not so easy to change, so come back to that one!
3) Below and behind the crankshaft pully is the oil pump cover plate. This is about 6" x 4" and is fitted with four (13mm?) nuts. They are special nuts with a sealing ring (a bit like a 'nylok' nut, if you know what I mean?) fitted on the ENGINE side of the nut. When ever they are undone they should be replaced with new ones but often are not. Sometimes garages who are unfamiliar with these engines put on the nuts (old or new) with the sealing ring on away from the engine - not good! So check the nuts are on the right way around (poke em with a pointy screwdriver, you'll soon see if they are on the right way around).
4) The same oil pump cover has a very thin paper gasket behind it, so the oil could be leaking from between the cover and the crankcase (engine)
5) The base of the oil filler tube is mounted to the lower offside of the crankcase, again, two (13mm?) bolts/hex heads and a gasket. Check the tightness of these two fixings.
Is your oil leak fresh clean oil, or just a cruddy/oily mess on engine?
The best way to trace such leaks is to warm engine, then brush on a good degreaser (Gunk etc) and leave for an hour, then brush on again, and leave....then...you guessed it......until you can use hot soapy water and detergent (washing up liquid) followed by a good rinse off. Allow to dry, then wipe, and clean again. You should be able to see the various joints well then. THEN check for tightness, as when you do, you might see oil squeezed out of joint (albeit a small amount) - if you do, sort that gasket.
Hope this helps, keep us posted.
