Coolant system maintenance

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Andy284

Andy284

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Aug 25, 2009
8
Hunter 28.5 Lake Perry KS
Hello all, I have a question regarding my yanmar 2gm20f coolant system.
I decided to change the coolant in my trusty diesel, this is my first time since I own this boat a Hunter 28.5
I flushed the system with containers for proper disposal but also to measure how much mix I would need to put back in.
I measured just shy of one gallon (including the expansion cup), then I filled the system with fresh water and to my surprise the system only took less tha 3/4 gallon before splashing out ot the filler cap.
How is this possible???? My experience with cars is that I usually the system takes more that not less coolant.
I flushed the fresh water and replaced with coolant with the same result,
Any ideas???/

Thank you!
 
Alan

Alan

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Jun 2, 2004
4,174
Hunter 35.5 LI, NY
You have an air lock somewhere in the system. If you run the engine to operation temp the thermostat will open and allow complete circulation and probably bleed the air off allowing the coolant to displace it. If not it may be necessary to manually bleed the hot water heater.
 
Warren Milberg

Warren Milberg

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Dec 1, 1999
2,391
Hunter 28.5 Chesapeake Bay
Alan is right, you've air somewhere in your system. Here is what I would try: start the engine and let it run for 10 min or so to get up to regular operating temperatures and to open the thermostat. Then, with the engine still running, open the radiator cap for the fresh water cooling system in the starboard lazarette. You may be able to slowly pour more coolant into the system as it circulates. I've done this a number of times on my boat.
 
S

s sauer

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Jun 4, 2004
844
Hunter 28.5 Tolchester, MD
You can remove one hose that circulates hot water to the hot water heater and fill from that point above the thermostat, then run the engine to 'burp' the remaining air out of the system. I've found that with the heater hoses, it takes a little more than one gallon of premixed antifreeze.
 
Andy284

Andy284

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Aug 25, 2009
8
Hunter 28.5 Lake Perry KS
Thanks Warren, it worked like charm. Just as you said, I was able to almost empty my container with the mix. I got about one inch left in the bottle that I am sure will take it next time I run the engine.
Thank you for the tip.
 
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