"you can pressure test the clo
"you can pressure test the closed cooling loop just like any auto radiator.
check you gear and engine for water in the lube oil (via dipsticks) - elevated (overfull) levels indicate water, usually. This is most likely due to a leaking oil cooler. (excessive 'condensation' inside the oil fill cap is another indicator.)
Both gear and engine lube pressures in the coolers exceed the raw water pressure -> if there's a leak, the oils go into the cooling water and wind up in the exhaust. Once shut off, the pressures subside and between gravity and drain back of the oils, the water enters. This is something that you want to resolve immediately."