Detroit diesel closed loop cooling questions

1) what level should I fill the cooling water reservoir tank up to? I have given different answers. Fill to the top or fill to about an inch (1/2 of index finger) to the top?2) my delivery captain told me to fill the reservoir with water. Shouldn’t I fill with 50/50 water and antifreeze? Or maybe top off once with water and next top off use antifreeze to try and keep the mixture close to 50/50?3) Does the reservoir end up being pressurized when the coolant is hot like a car radiator? It should only be opened when engine is cool? 4):Where does the coolant go? I did a 35 hour delivery run. At the end of the trip both engines cooling water levels were about 1 inch down. I have 1988 67’CPMY with DD12v71Thoughts?Thank you

A coolant recover system was not a factory option when most of these boats were made then. A check when the engine is cold, fill the expansion tank up with water or coolant mix.
When the engine heats up, coolant expands a bit, the cap vents some of this out to ensure no trapped air, a mini thermostat in the cap then closes and forms a closed system. The cap then regulates the system to a set pressure (DD 7 psi).
The next day when cold, the expansion tank will be down about an inch.

IMO, as a delivery captain, add water or coolant every morning (when cold).
As a delivery captain, add oil to the cold engine even if just 4 drops low.
Never try these check when warm or hot.
Record your engine services. Submit a report when delivery complete.
It is the owner who can decide to operate out of spec and how far, not a delivery captain.

Maintaining a 50/50 mix does not have to be a science. In Florida, I mix to 60-65% water.
Remember; water cools the engine, not antifreeze. Antifreeze keeps rust down, lubricates the water pump seal, helps keep hoses-seals-gaskets supple and then reduces the coolant from freezing.
Remember; ad distilled water to 92 and 53 engines. 71s are tough and don't require this extra whimp effort.

Without a recovery bottle, the wasted coolant drains into the bilges. Below the cap is the vent path. You can follow this to the bilge or recovery bottle.

As on our boats, our shop often installed coolant recovery systems on our customers engines and gen-sets.
Also, DD air-box check valves and slobber recovery systems to further reduce snot in the bilges.

These don't have recovery tanks, so just fill it up to the top and the engine will self-regulate the level by dumping the extra into the bilge. Detroits are super simple.

Quote:

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Originally Posted by cww

These don't have recovery tanks, so just fill it up to the top and the engine will self-regulate the level by dumping the extra into the bilge. Detroits are super simple.

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My 46 year old, 12V71TIs have recovery bottles. Installed near 18 years ago.
Air box drains updated. Our bilges are clean and don't stink.
Williams 39 year old, 12V71TAs have recovery bottles. Installed about 6 years ago.
TA's already have the check valves and return system.

Quote:

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Originally Posted by Kquaine

I did a 35 hour delivery run.

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Early this morning I may have read this wrong.
This is your boat, your not just the delivering captain.

If you would like, I can offer some pictures of some recovery bottle installations. Never have to open that tank cap again.

Please send pictures of recovery bottles, mine drain to bilge, hence keep at finger tip length level to prevent over flow.

Thank You!

my 871s have had two gate valves per engine threaded into the top inch of the heat exchanger tank fresh water side. One valve is plumbed to the potable water system and can be opened to add water to the tank. The second valve is to open when filling the system from pressurized water, coolant will literally come out and you know tank is full. Both valves are normally closed. I don't use them much but nice to have for an emergency method of adding water to system quickly and conveniently.