Yanmar 4JH3-HTE

[Alan Havelock]

Hi, looking at a sailboat that has a Yanmar 4JH3-HTE (100 hp) in it. The antifreeze overflow tank is not attached to the nipple underneath the fill cap but somewhere near the front left of the engine (maybe near the thermostat??). When you open up the fill cap to check the level it is not up to the top as it would be on my Westerbeke 40, it is about 2″ down. The engine was installed 20 years ago and seems to work fine and seems well maintained. The owner says the mechanic told him to just add any fluid needed via the overflow tank and that’s what he has done. I topped it up via the fill cap because that’s what I have always done but after the engine was warmed up some fluid came out of the nipple at the cap so maybe we overfilled it and the real level should sit a couple of inches down?

Anyone know why you would plum in the overflow tank somewhere other that the fill cap output?

Anyone see a level that is not to the top of the fill cap as normal?

Thanks

Topic

[Tony Athens]

Your system was designed to operate with a non-pressurized Plastic overflow bottle kinda like 99.999% of the cars out there.. That way you have visual of the coolant level.  Cold,  all is 100% full in the engine -Plastic bottle maybe 50% full.. Hot the bottle rises a tad, & w/ the engine cools,  the bottle goes back down……..Too simple when all is right and the engine is empty of air and has a proper coolant cap. Sounds like you do.

[Author]

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