Ive been having a mysterious coolant leak for about a year now. First time i brought it in the dealer put the pressure tester on over night, no drop in pressure, no leak right? About 8 months later my surge tank was empy again. Took it in to a different dealer, turbo coolant line leaking. Figured i would tackle it, upon removal found coolant blowing out of cyl 1. At this point i was using a surge tank per week. Took it back to the dealer as they clearly were missing the real issue. Head gasket or more likely a cracked head.