Thanks for the warning Giallo - I bought a size 15 ring spanner shaped like this one (I'm not sure if there's a special name for it):
Deep Offset Ring Spanner - Deep Offset Ring Spanner Exporter & Manufacturer, Ludhiana, India
and that worked well.
Took off the fixed tensioner and then the cambelt cover and ran the engine again, to look if there's any leak above the crankshaft pulley. There was a good deal of black oily gunk all over the place, but even while the oil was already dropping down on the concrete, I could see no traces of fresh oil above the crankshaft; so I guess it's really the oil pump seal.
But the amount of old oil all over the place is really astonishing. I'm guessing that the oil has been slowly leaking for some time and as it found its way on the belts and pulleys they have carried it all over the side of the engine. What do you think?
At this moment I'm waiting for Polydrive bits that I have ordered, so that I can continue with taking off the crankshaff pulleys. (I tried taking the screws off with regular screwdriver, but no good and I don't wab't to round them off while trying). In the meantime, here's a few pictures that I took for anyone who might find them handy:
Pulleys with aux belt off:
(The wet spot on the crankshaft pulley is not oil, just WD40 as I was trying to loosen the screws)
With aux belt fixed tensioner off:
The aux belt fixed tensioner:
The cambelt cover:
And finally the cam belt pulleys:
Also the tool 1.820.617.000 that Giallo was writing about about arrived today, I ordered it from the local Alfa dealer:
I was kind of hoping there would be a manual included in the package but there was none so I need to figure it somehow
I guess the ring on the right side, with eight holes, attaches to the cambelt crankshaft pulley, with the screws that now hold the aux belt pulley, but am not sure where does the ring on the left side fit. I'll see if I can find it somewhere, but any tips are of course welcome