I owned this 5 series 535i (2009, E61) for about four years now. I hate to tell you this, but so far it is the most unreliable BMW I ever owned. I love the utility of E61, xDrive system is awesome, wagon styling is way superior to sedan's (personal opinion), but this (N54) engine...

The E61 started to leak the coolant. Turned out that water (coolant) pump lasted only 36k miles...

To find the problem I used:
Rented:
https://www.autozone.com/loan-a-tool...ure/449951_0_0
Bought:
Gunk engine degreaser (sold almost everywhere)
UV Dye (sold almost everywhere)
UV Leak detection kit (sold almost everywhere)


Why I haven't kept my 2006 530 wagon