Ruby, the daughters 850 but with a 1098 has low oil pressure.
When we bought her she had no oil or water gauges (typical of an 850) and one day Ruby arrived home smoking and boiling.
A blown head gasket after it ran out of water due to a faulty thermostat.
Bores were still OK so we had the head reconditioned and I checked the block for flatness and bolted it back together.
At this time we also installed mechanical oil and temp gauges.
Started her up and all seemed OK except she had low oil pressure, 20 - 25 cruising and 10 - 15 at idle.
I was told it had worn bearings and needed a rebuild.
A member on here in another thread said they had a Cooper S that had low pressure from new and during a rebuild found that the relief valve had never been seating properly.
Well guess what, neither was Ruby's.
There was a shiny spot on one side of the seat and a shiny spot on the opposite side of the body of the relief valve.
Attachment:
IMG_1902.JPG
Attachment:
IMG_1901.JPG
Bedded in a new valve and spring and now Ruby runs at 65psi on the freeway and 25 -30 at idle.
Just saved a few thousand $.