Timing issue during exhaust valve job

[difflock54]

Reading the blurb again on the link I interpreted it as the exhaust cam with the cam sensor attached requires a rear seal.
The inlet cam appears not to require one however for an S40 4 cylinder. 2001.
It is indeed a bit confusing and strange but it would explain the absence of a seal previously and from the pics posted it even looks quite dry, although dark oil stained.

[difflock54]

vvt_hub_front_rear_cam_seals_front_crank_seal_servicing.pdf

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I just recalled having downloaded a pdf some time back which describes almost all of this work for a 2003 engine.
I don't recall the name of its author unfortunately but all credit naturally goes to that person.
Stage 37 and pics describes specifically that a seal is not fitted to the rear of the inlet cam.

Hope this will help you.