Yep No 2 is the rear oil seal, leakage there can occur there I believe?
No 7 is the thrust bearing, as you said when the turbo creates pressure it wants to move back, this absorbs the load I believe. On the turbo I disassembled (T03 similar) the thrust bearing was a bronze bush I believe, and there was what looked like a carbon? seal behind the bush/bearing.
I would suggest the oil leakage would be the result of the pressures created, very high vacuum and also boost. As I see it the compressor side could allow oil to be burnt under vacuum, and the exhaust side I'm not really sure to be honest (someone enlighten me?!), I would have thought that the exhaust would always have positive pressure, I maybe wrong on that thought?
Cheers
Wilbo
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