So my 05 S4R is losing coolant via the expansion tank. The coolant boils over so I got a leak somewhere. Ordered a new rad cap already and havent tested it yet. Head gasket is ok, I did a combustion test and it came out negative. Oil at sight glass is also clear. So it must be at the hoses or rad cap. I found this while snooping around (see pic). Parts list says its a water output connector... what is this thing for?
Thanks!