According to the Messerschmitt Bf109 Owner's Workshop manual
http://www.amazon.com/Messerschmitt-.../dp/1844256421
in the G series "four coolant shut-off valves are fitted into the delivery and return lines, and are operated by two handles in the cockpit" (p. 123) meaning that if there was a coolant leak, or a pipe had been shot up, the pilot could isolate and shut down the affected circuit, thus preventing total coolant loss. The F series had them as well, but I don't know about the E series.