On inspecting the sump it turns out the ring terminal for the earth strap has broken, it was in place so that you could not see it had broken. There was a bit of contact but not much. This is the cause of the high oil pressure. Not much earth gauge OK when you put it on ignition 2, run the starter and it screws that up so the pressure goes up. Disconnect it and no earth = gauge on highest setting.
The also means the starter does not run properly as it doesn’t get enough power.
Took the sump off. No obvious marks in any of the bores from the bottom. Push in the oil return and the oil runs out fine, oil pump seems to be OK.
Added a temp earth strap and now the starter runs fine turning the engine over without any problems (no plugs) – no odd sounds from it either.
Hypothesis is airlock (driving up hill), overheat and then unable to run anything due to the earth strap.
Seizing probably due to small tolerances and overheat. Need to pull a cap off check a shell for damage.
Doesn’t look as bad now as it did initially. I’m going to do have more of a look around, get a genuine water pump from BMW as the one I have makes a noise and a new sump gasket, new oil and filter and see how it goes.
