Cool!  Glad it wasn't any more serious.

Cheers,
Ken

This leak ended up being the oil pressure sensor. $20 fix!

Fluorescent dye oil leak detector kit, used with a black light, quickly pinpoints the source of an oil leak.  Available at a car parts store near you.  Used it on my classic mini more than once with success.   We might have something in common after all.......

The oil filter housing can be serviced from underneath the car, although it helps to have small hands...  It 'can' be done without removing the subframe.  A lift definitely helps....

Ken

OK.. I am leaning towards ordering the whole oil filter housing kit which includes the pressure sensor and oil cooler.. this way I know I'll only have to do the work 1 time.. hopefully,, LOL

Next question would be..
Do I need to drop the sub-frame to replace this or can it be removed from the top? I know the oil filter housing gasket can be done from the top.. but can it be removed and replaced from the top??

I think you are pretty close in your diagnosis.  The oil cooler O-rings and the o-ring on the oil filter canister cover and the oil pressure sensor would be suspect - these are the areas that have direct access to oil.

Ken

I’m having a hard time fixing a R53 oil leak.. Oil is leaking down onto the rear motor mount. It is very hard to see in this area.. Best I can tell it is coming from the area where the oil filter housing/oil cooler is. I replaced the oil filter housing gasket and it now appears dry where the filter housing bolts to the engine block but it's still leaking pretty bad from somewhere in this ara. Is it possible to leak at the oil cooler? Would bad oil cooler O-rings cause oil leak? Oil pressure sensor?  What else up there can leak badly? I looked at the valve cover gasket and it looks pretty dry..

I have replaced:
Oil filter housing gasket, oil pan gasket, crank position sensor O-ring. And last time I had it apart it looked dry behind the crank pulley.

Any advice would be greatly appreciated.