Anti siphon valves
The problem created from a failed antisiphon valve in the cooling water line is not from spraying water into the air intake. It comes from water siphoning back into the engine through the muffler and the exhaust valves. It usually is accompanied by a failing water pump. If your water pump is perfect (few are) it serves as a dam to prevent water from siphoning from the sea into the engine which is mounted below the sea's surface. To counteract this siphoning effect, the discharge water from the engine is run to a point above sea level (higher the better) where and antisiphon, or air break, valve is installed. the water is then piped into the exhaust to be dumped overboard. when the engine is running, the water pressure from the engine to the exhaust is supposed to keep this valve closed and the water zips right on by. When the engine is shut down a siphon is set up between the higher sea and the lower exhaust mixing elbow. The lower side pulls the water up and over the vented loop (antisiphon valve) creating a low pressure in the tube. Now is when a properly operating sntisiphon goes to work. It lets in a little dab of air which interrupts the vacuum of the siphon. The water on the sea side drops back ino the sea and the water on the engine side drops into the water lift muffler. To fine your antisiphon valve, follow the hoses either from the mixing elbow or from the engine discharge. Either, or both, will lead you to the valve. It can be tested by removing it and blowing into the pipe side. You should not be able to blow. You then suck on it and you should be able to get air. You have my permission to wash the whole thing off before this test. Now you know what an antisiphon is for, where to find it and one of the reasons why they put that waterlock muffler in the system.
