I’m stumped

I live in Alaska and this weekend I went to my boat which is on the hard. (The boat is a 1978 37’ pacific trawler.) I hooked a portable generator to the ship to shore cord and I left everything off at the panel except the power to my hurricane heater. Turned the burner on and went to work on the boat.

When it came to temp of the t-stat setting, I needed something out of my truck and when I exited the boat I noticed that a one inch thru hull on the stern was dripping glycol out of it. A bucket and absorbent pads were placed there and it was coming out about the diameter of a pencil. When I turned off the burner it stopped. I crawled into the lazzarette and there was a heater hose from the thru hull to the bulkhead. When I entered the engine room in the rear I lost it due to it being behind the water tank. The heater has a glycol receptacle that was full. a small overflow jug had about one inch of glycol in it. The system also is hooked to a tank that resembled a twenty pound propane tank with a bleeder valve on the top of it. I opened it and couldn’t hear any air and no glycol escaped from it.

Every time I turned on the burner, the flow would come out again and I captured about a gallon of glycol. I didn’t see any heater hose running from the lazzarette to the system and I am completely out of ideas and was hoping somebody might be able to give a pointer or two. Thanks!

what is the thru hull for ? you have a leak you could use air to pressurize the system .but you would have to be careful not to get it over the max system pressure . that would probably push all your liquid out but when you get to an air leak you may be able to here it. mine has a radiator behind the water tanks . and in the engine room . all my hose need replacing it is brittle and cracks easily .

Thank for your reply Tim. The thru hull is connected to a heater hose. I thought this was a closed system and I can’t figure out why it’s coming out.

It might be a vent for a pressure relief valve which has lifted.

Check on the glycol tank for pressure relief valve (similar to the one on a hot water tank).

Thanks, didn’t see one but I’ll check again.

Any chance that there is an expansion tank that got a hose knocked loose?

There’s an overflow tank, off the reservoir tank, and an expansion tank. Everything looks good, the expansion tank has a keyed needle valve on top. I assumed that unscrewing it would release some air, or at least a little glycol, but neither happened when I opened it. I don’t believe it’s pressurized except to hold some air from air in the zone lines. I guess what has got me shaking my head, is that it is closed system and it’s coming out of a heater hose out the stern without a pressure valve that I can find.

Hey Spotter,

Just to sanity check a bit...you mentioned that everything looks good. Does the loop and/or expansion tank seem to be low on glycol? Is it air daming anywhere?

The expansion tank is full. I just pulled up the schematic and operating instructions and they don’t have a thru hole bleed off on any schematic. What I called the glycol reservoir is actually called the expansion tank and nowhere is the receptacle resembling a 20lb propane tank that is installed to the reservoir even listed. As I live 350 miles from the boat I’m unable to check it every time I have a new suggestion or idea, but I will check it all when I go down in two weeks. Thanks again to all who responded, it is much appreciated.

-- Is this a new to you vessel?
-- Is the heater exhaust line per chance connected to the leaking through hull?
-- Is the through hull connected to a bilge or shower pump that receives coolant system overflow?
-- Cold winter and something froze?
-- Is the expansion tank fitted with a functioning radiator cap and overflow container?

Sunchaser, I’ve had the vessel for two years gunkholing Prince William Sound most of the summer. The heater exhaust and fresh air inlet is a large thruhull that incorporates both in one. No bilge or shower pump connected to a coolant system. As there is glycol in the system there was nothing that froze. Moderate temps on the coast. The expansion tank is fitted with both a radiator cap and an overflow container.

Are you sure this is from the heater, and not winterizing glycol from somewhere else? If so, any chance that the thru hull is connected to a bilge pump or sump pump somewhere, you have a leak in the heating lines, and it is getting pumped out?
The PO of our boat did something I couldn't understand at first, but now think is pretty smart. The engine coolant is the red stuff, and the hydronic heat system uses the green stuff. It's an old boat and both systems leak, but at least now I can tell which one is leaking just by looking at coolant color.

BTW, the propane-looking tank with the air fitting on top sounds like an accumulator tank. They are installed in some of the hydronic systems to help with coolant pulsing.

Thanks Stripper for the proper nomenclature! Now I won’t sound like a knucklehead. It’s not rv glycol so I’ll check when I get back down there.