Same leak happened when I was changing all my coolant hoses. It didn't leak before I unplugged it, so unplugging it broke whatever deal was keeping it from leaking: the o-ring was cut. I couldn't find it sold separately, so I got a whole new sensor (from FCP Euro I think) which wasn't that expensive.

Sent from my SM-N950U using Tapatalk

__________________
Mike - Greater Seattle, WA, USA
2002 E53 X5 4.4i Sport Pkg Black (daily & tow vehicle)
2003 E53 X5 4.6is Estoril Blue (to replace 4.4i soon)
2002 E53 X5 4.4i Sport Pkg Silver [sold]
2001 E46 325Ci Hardtop 5MT Topaz Blue [sold]
+ Toyota track/autox/rally cars: MR2 (x2), Celica AllTrac Turbo (x3)