Ok so here is a head scrtacher.
My wifes 90' 560sel has had a hyrolic oil leak that has been on my list to take care of. Well she brings it home the other day and says my car is making a moaning noise. So I fire it up this morning and it's actually more like a train whistle sound just sitting there in idle. Fluids look reasonable noise seems to come from under the front but also the rear of the engine. Belts are tight, all moving accessory pieces (alt, AC) move freely. The noise is the same in all PNDL positions.

I've got the underbody soaking with engine degreaser, so I thought while I'm waiting I would check and see if anyone had ever heard this before.

Regards,
Bob