Expansion tank location Yanmar 4JH3-HTE

[berwick]

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

[pcmm]

My Yanmar 4JH2E ( earlier version) has the expansion tank connected to the nipple on the heat exchanger. Unless there is another pressure relief valve elsewhere in the system I'm not sure that this Yanmar is connected up correctly. The coolant should be filled right up to the pressure cap on the heat exchanger.

[berwick]

Well that's what I thought too as was my W40 but this was a new install so not sure what to think.

[skipperpete]

Originally Posted by berwick

Well that's what I thought too as was my W40 but this was a new install so not sure what to think.

That hookup means your engine fw cooling system is unpressurised assuming its the yanmar expansion tank and not a Volvo tank. Could this unusual connection be somehow related to an elevated calorifier tank?

[Ericson38]

Originally Posted by berwick

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

The fluid that came out the nipple at the top cap due is to coolant heat expansion (normal and a good sign), and it should have been routed to the overflow tank via hose. What is currently connected to the overflow tank via a hose is a drain petcock on the front of the engine.

https://www.bing.com/images/search?v...t=0&ajaxserp=0

I doubt the coolant has been changed recently, since there seems to be confusion with the current owner on how this works.

Should be connected like this image shows-

https://www.bing.com/images/search?v...t=0&ajaxserp=0

[berwick]

Just had a tech to the boat, what he did was put a higher pressure cap on the tank and blocked off the nipple. There is another overflow tank that is mounted higher up which sort of takes over the normal pressure cap as the hot water tank is located a little higher than normal thus the addition of this other overflow tank that is higher. There is also another smaller overflow tank that keeps this higher overflow tank topped up and allows for the expansion. I think it makes sense to me now, they ran it and it keeps the lower tank topped up now.

thanks

[skipperpete]

Thanks for the update berwick, pleased to hear you got it solved.
Pete.