Re: Another 470 with a coolant problem
Have you checked for water in the oil or on the spark plugs? This is an indication that the elbow may be rotted through. If everything is dry, it is likely that the leak is below the exhaust level. Remove the spark plugs and give the engine a short crank. No water should come out! If it does, then it is likely that the leak is above the valve level (exhaust manifold, etc).
On my 470, the raw water comes in and goes through a heat exchanger under the exhaust manifold (big round tube with hoses) and then exits through the exhaust manifold. I suspect that yours is the same since you have to add antifreeze. Another thing to check is the heat exchanger. There are gaskets on each end that can deteriorate and leak between the raw water and coolant. Again, the cheaper thing to look at first. Also, the heat exchanger can rot through internally. You can check this by removing al the hoses and filling up the coolant portion and look for water coming out the raw water tubes. Be sure to drain the exchanger before doing this and make sure the drains are closed! Used exchangers are $100 or so off eBay.