The CDC Cyber mainframes installed at Fylingdales in the early 80s were liquid cooled. I don't recall any incidents with the cooling - leaks, etc. Also I recall being told at the time that volume for volume liquid cooling was 5 times more effective than air hence it's use despite the attendant risks from plumbing within the electrical cabinets. I stand to be corrected on this as it's 30 years ago, but I'm pretty sure 5x was the factor.