Water Heater Air Lock

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wfcreadon

I ran into a problem with heating my domestic hot water from the engine loop through it. I have an air lock, as my top hose of my hot water circulation hose is higher than the Radiator Cap. It would be easy to open the hose clamp and push a screwdriver down it and bleed until I get a stream of antifreeze. In the mystical wisdom of prduction building the hot wateer heater cannot be accessed without destroying the aft bunk molding. I can cut an access port but I am looking for another solution. Any ideas???
 

RichH

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Feb 14, 2005
4,773
Tayana 37 cutter; I20/M20 SCOWS Worton Creek, MD
Put in a 'drain cock' .....

,,,, in the 'highest' location of the circuit. Automotive supply stores sells these (plastic) for adding 'flushing' chemicals and 'backflushing' to radiators and heating circuits in automobiles .... just be sure the opening is UP so the air can come out.
 
Jun 7, 2004
944
Birch Bay Washington
Are you sure that you have an air lock?

Mine does not and it has never worked properly. I have bled air and tried everything else I can think of and it still will not work. I have a Yanmar 3HM35F and the circuit only gets a little warm. It actually cools the water in the hot water heater when I run the engine. I am planning to completely redesign the cooling system just as soon as it gets to the top of my list.
 
Dec 2, 2003
209
Hunter 34 Forked River, NJ
When I installed a new

hot water heater this spring, I plugged the hoses that run to the engine, so as the water did not run out. I removed the old unit, and after I installed the new heater, I re installed the lower hose,added a short piece of hose to the upper inlet, then I filled the heat exchanger loop in the heater with a water/anti freeze 50/50 mix with a small funnel in the temporary hose, when full, I quickly removed the temporary hose, and fitted the remaining hose from the engine. I had no problems with air trapped in the system.
 
Jul 17, 2005
586
Hunter 37.5 Bainbridge Island - West of Seattle
Is there an air bleed drain cock?

Look in the engine compartment. Somewhere next to the engine, there will probably a air bleed valve in the heater hose. On our 37.5, the heater hose in the engine compartment is the highest point in the entire water circuit. Run the engine until warm, and open the valve to let out any air pockets. I have flushed my coolant quite a few times, and have never had an air pocket. If there isn't a air bleed valve, it is easy to install one.
 
Jul 25, 2005
15
Oday O'Day 35 Kent Narrows, MD
An air-bleed petcock is the answer....

....if your diagnosis of the problem is correct. When our boat was new to us, I replaced both coolant hoses to/from the water heater and had a similar air lock problem. A number of solutions were suggested, including running the engine with the coolant cap removed, to boil the coolant and bubble off any trapped air. Nothing worked until I discovered the petcock on the coolant hose at the water heater. It doesn't take much air in the line to cause the problem. Seems like have that bleed point will be useful again when you change coolant, hoses, etc.
 
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