Yanmar 3GMF losing antifreeze

Don Crowther · May 19, 2014

Could be the seals in the heat exchanger. The anti-freeze could be leaking past and exiting out though the exhaust.

kloudie1 · May 19, 2014

Lots of possibilities.. from the least expensive:
* Leaking overflow tank hose or tank.
* Leaking heatex cap gasket.
* Leaking heat exchanger end gaskets/O-rings
* Leaking heat exchanger tube
* Leaking head gasket
Could get worse, but those are the usual suspects. If there is no visible leakage and you are sure of that, then the coolant is probably going out with the sea water. The suspects would be the heat exchanger gaskets or the tubes themselves..

Don Crowther · May 19, 2014

Claude
Won't a leaking head gasket cause overheating?

kloudie1 · May 20, 2014

Hey, Don.. it certainly can, but many times does not until the coolant gets really low.

bryan crites · May 20, 2014

antifreeze leak

I had the same problem on my 84 34foot hunter. I put red die in the heat exchanger , then noticed the red die in the bilge. Located a pinhole in the water heater heat exchanger hose. Replaced the entire hose, and solved the issue.

Jeff10528 · May 20, 2014

Jed10444 said:
I have a yanmar 3GMF on my 1983 34' hunter. From time to time the antifreeze in the heat exchanger empties. I don't see a hose leak. Could anyone please offer any input. Thank you

Last season I noticed similar symptoms in the coolant reservoir in my H430 with Volvo Penta power. A small leak was found on a hose fitting on the heat exchanger. Finally, while under power for only an hour, and going below to find the cabin to be unusually hot and smelling like hot metal, I killed the engine and after a short wait, opened the engine compartment. I was hit with a face full of steam. That ended our season. Other than the already mentioned leak nothing was found. We were concerned about the condition of the engine so had our yard pull the engine to allow them to examine the oil pan and repaint areas where the paint had peeled off. No metal shavings were found and miraculously, the oil had not been burned.

The big find was only made possible by the removal of the engine. Hunter had routed the coolant hoses between the engine and water heater through a roughly hewn hole in the main stringer. After 15 years and 240 engine hours, vibration had sawn the hoses open enough to dump all of the coolant into the bilge. Those holes have been fitted with protective sleeves and hoses with a steel reinforced type.

Hope this helps.

richk · May 20, 2014

Jeff10528 said:
Last season I noticed similar symptoms in the coolant reservoir in my H430 with Volvo Penta power. A small leak was found on a hose fitting on the heat exchanger. Finally, while under power for only an hour, and going below to find the cabin to be unusually hot and smelling like hot metal, I killed the engine and after a short wait, opened the engine compartment. I was hit with a face full of steam. That ended our season. Other than the already mentioned leak nothing was found. We were concerned about the condition of the engine so had our yard pull the engine to allow them to examine the oil pan and repaint areas where the paint had peeled off. No metal shavings were found and miraculously, the oil had not been burned.

The big find was only made possible by the removal of the engine. Hunter had routed the coolant hoses between the engine and water heater through a roughly hewn hole in the main stringer. After 15 years and 240 engine hours, vibration had sawn the hoses open enough to dump all of the coolant into the bilge. Those holes have been fitted with protective sleeves and hoses with a steel reinforced type.

Hope this helps.

Same thing happened to me on my previous boat....however the w/h wasn't oem, it was installed by p.o.