Loss of coolant in fresh water system

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healey1959

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Jul 6, 2009
7
2 30 New London, CT
A week ago my Catalina 30 Universal diesel overheated. Since I didn't have any history of when the thermostat was last changed I decided to change it. After changing the thermostat and bleeding the system it tested OK at the dock. Taking the boat out and running the engine for about a total of 40 minutes it appeared that I solved the problem. When I was going to use the boat a few days later I checked the coolant level and it was low. I had to add about 3/4 of a gallon to bring the level back up. It appears that I am losing coolant when running under load. There is no coolant in the bilge. No signs of leaks I think it must be mixing with the raw water and going out the exhaust. What steps should I take in tracking down this problem? Past history of the cooling system is in 2004 the water pump, circulator pump, all hoses and hot water heater was replaced, also the heat exchanger was upgraded to 3"
Any help will be appreciated.
 
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dsavlin

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May 23, 2009
5
2 1988 C27 Tall Rig Montrose Harbor, Chicago
If it's not ending up in the bilge, then there's really only two places it could be going: out the exhaust (failure in the heat exchanger loops) or into the oil (head gasket failure). If I were in this situation I would try checking both: maybe use a bucket to capture some of the exhaust water to see if antifreeze is showing up, and use an oil extractor to drain the oil and see if the oil is "milky" with antifreeze.

The only reason I mention the head gasket failure is that you said the diesel overheated, and gasket failure seems to go hand in hand with damage resulting from overheating.

What symptoms did you have that let you know it was overheating? High temperature on the gauge, thick smoke, etc?

I am not an expert but these are the things I've learned over the years to look for. Good luck!
 
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healey1959

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Jul 6, 2009
7
2 30 New London, CT
Thanks

dsavlin said:
If it's not ending up in the bilge, then there's really only two places it could be going: out the exhaust (failure in the heat exchanger loops) or into the oil (head gasket failure). If I were in this situation I would try checking both: maybe use a bucket to capture some of the exhaust water to see if antifreeze is showing up, and use an oil extractor to drain the oil and see if the oil is "milky" with antifreeze.

The only reason I mention the head gasket failure is that you said the diesel overheated, and gasket failure seems to go hand in hand with damage resulting from overheating.

What symptoms did you have that let you know it was overheating? High temperature on the gauge, thick smoke, etc?

I am not an expert but these are the things I've learned over the years to look for. Good luck!
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Thanks for the quick reply. I noticed the problem on the gage as I was coming into my marina. I'm going down to try checking the oil and exhaust water tomorrow. If there is coolant in the exhaust is the a way to check the heat exchanger?
 
Tom J

Tom J

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Sep 30, 2008
2,325
Catalina 310 Quincy, MA
I'd run the engine again and recheck the coolant level. Sometimes the engine has to run several times after emptying the cooling system before the level of coolant in the expansion tank stabilizes.
 
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healey1959

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Jul 6, 2009
7
2 30 New London, CT
Went to the boat Tuesday and checked the oil, level good, no foam, no signs of coolant. When I checked the bilge and took a closer look I noticed coolant. I refilled the coolant and started searching for a leak. The coolant level dropped when the engine hadn't been run. Spent time checking each hose and finally found a hose going to the hot water heater had a hole in it. Replaced the hose and ran the engine at the dock bleeding the system and topping off the coolant.The temperature stayed at 160. Rechecked the coolant level and it was good. Yesterday I went down, no coolant in the bilge, coolant level good. Took the boat out on the water and ran the engine for 45 minutes under power. temperature stayed at 160.
I think the reason I didn't notice the coolant in the bilge before was the bilge pump must of pumped out most of the coolant. Thinking back I must of just open the bilge for a quick look and was looking at the level more than the color.
Lesson learned. Take time with problems and do a closer inspection of situation.

Thanks for the help its great to have a resource like this from owners that have been through similar problems. Experience is the best teacher.
 
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