Again thanks to all for the info and suggestions.
Latest update, I pulled the heat exchanger and it's fine. Visual
inspection no
corrosion or holes to be seen,
DIY pressure test passed, filled the fresh water side with water and let it sit for two days and not a drop leaked out.
So best guess, based on all comment, wasn't it.
Summary of the status so far.
- Heat exchanger checked very closely, appears good.
- No obvious or visible leaks anywhere in the system. Considering the amount of water I'm losing I'm pretty sure it would be easily visible.
- Crankcase oil is crystal clear so water is not ending up there.
- Based on my logic and comments here, IE pressure in the combustion chamber is 100 times higher than the pressure in the fresh water cooling it is very unlikely the water is going into the combustion chamber.
- Fresh water header tank. The exhaust cast iron elbows leave the side of the block and bolt to the bottom of the header tank, collect into a common pipe the exit the back of the header tank to the mixing
elbow. This seemed like another possible source of the problem but I pulled the header tank off an old W58 I
purchase for
parts and the
fresh water tank is a solid casting and the exhaust pipe is in a channel along the bottom and does not penetrate into the tank so very unlikely this is the problem.
If the head gasket is compromised I can only think of three things that are theoretically possible.
1. Water going into the combustion chamber. Unlikely
2. Water going into the oil. Don't see it.
3. Water leaking out the side of the block. Don't see it.
Going back to the
boat today to reinstall the heat exchanger and try more testing.
1. Even though I seem to be losing a pint or more in 15 minutes run which I think would be visible the next step will involve a UV leak
inspection.
2. Retrace the entire cooling system to confirm any other place the water could go that wouldn't be easily visible.
3. Check the header tank to confirm my theory that it is not the source of the problem.
4. Do a pressure test on the system. I can borrow a radiator pressure/leak detector that installs where the radiator/pressure cap fits but wondering what I could learn with it. I already know I'm losing water, I need to know where. If there is a leak in the head gasket if I turn over the engine with the tester connected would I see pulsating reading? Someone suggested that a slow build up to pressure then stable would indicate a leak in the head gasket to a cylinder that would stabilize as the pressure built up but would that not depend on the position of the intake and exhaust valves?
What next?