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Author Topic: Disappearing coolant  (Read 163 times)

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Drhive

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Disappearing coolant
« on: January 14, 2022, 12:38:58 AM »

For what it's worth, I've just solved a mystery related to disappearing coolant.  My 34MKii engine was losing small amounts of coolant every time I checked, even though I only ever use the engine for getting to and from the marina, raising and lowering sails, and anchoring.

There were no signs of leaks on any of the engine hoses.  To check to see if perhaps it was evaporating, I put pieces of cardboard down at the bottom of the engine compartment, on both sides and under the belts, then ran the engine.  Again, no sign of leaks.  I also ran the engine with the coolant cap off to see whether there were bubbles, an indication of a blown gasket.  Nothing there, either.  And no, there was no spillage coming from the overflow in the lazarette.

I cleaned the bilge completely, and then ran the engine again.  This time I noticed coolant in the aft bilge compartment, but at that point there wasn't enough to leak through the passage hole to the middle part of the bilge. I couldn't see any signs of the coolant on the curved hull leading down to the bilge, so I put my hand through to feel for any coolant. When I did that I was very surprised (to say the least) that the whole top of my arm became coated with the coolant.  I then looked under the galley sink and found where the coolant hose runs through to the water heater.  But again, there wasn't any sign of coolant, that is until I felt around to the back of the hose.

It turned out that the hose had developed a very small hole at the edge of the tube running from the water heater.  It had been seeping from that hole around the back of the hose and down to where the hose goes through the bottom of the galley sink cabinet.  It then ran along the whole length of that piece of laminate until it came to the edge, and then dripped directly down into the bilge.

Needless to say, I was quite relieved, particularly since the worst case option would probably have been a leaking heat exchanger, which would have required a rebuild.  All that was required was cutting a larger hole in the back of the cabinet to make it easy to get at the hose, the cutting off of the damaged part of the hose, and resetting with a hose clamp.
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Ron Hill

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Re: Disappearing coolant
« Reply #1 on: January 14, 2022, 03:31:22 PM »

Drh: You are correct that the "worst case" was to have an internal leak in side the HX. 

However, You are lucky, because a "VERY worst case leak" might have been an internal leak inside the Water Heater !!
OR a SUPER worst case might have been inside the the engine itself!!!!    You are lucky that you FOUND IT!!!   :D :D :D :D

"Old Chinese Proverb" -- When that coolant recovery bottle level goes down - that coolant is going somewhere??????   :shock: :shock:   

A few "Happy" thoughts  :thumb:

« Last Edit: January 14, 2022, 03:37:55 PM by Ron Hill »
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Stu Jackson

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Re: Disappearing coolant
« Reply #2 on: January 14, 2022, 05:32:00 PM »

Congratulations for playing detectiove work and finding the culprit!  :D

It appears now that the Critical Upgrades topic is applicable to Mark II boats, too.  IIRC another Mark II skipper had earlier reported replacing his heater hoses.
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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KWKloeber

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Re: Disappearing coolant
« Reply #3 on: January 14, 2022, 07:06:05 PM »

Point of information for everyone (actually two POIs.)

A leaking Hx is basically a throwaway item. Yes it can *sometimes* be fixed but is typically not worth the cost.  OEMs were typically not copper-nickle (more expensive) and more prone to pin-holing (between the seawater and engine coolant sides) esp in saltwater.  Coolant doesnít end up in the bilge (it goes out the exhaust) so itís hard to diagnose w/o pressure testing the Hx.

A leaking WH (again, typically a pinhole between the potable water vessel and coolant tube) typically does NOT lose engine coolant - it GAINS engine coolant. Why?  The closed engine-coolant loop maxs out about 15 psi, and the hot water vessel is nominally at whatever pressure your potable water pump is set at (much higher than the engine pressure.)  So coolant canít push against that high pressure and get into the potable water side (good thing cuz itís toxic, so BEWARE if your potable water is unpressurized.)  The WH pressure can actually go much higher than the engine block*** (why the WH tank has a temp/pressure relief valve) so potable water can move in the opposite direction, sometimes with coolant ending up in the bilge or wherever the coolant reservoir bottle can overflow to (potable water pushes into the WH hoses, to the engine block, out the exhaust manifold pressure cap, to the coolant reservoir overflow.)

*** Why the check valve on the WH must be rated for WH use, and not the plastic ShurFlo CVs that are typically used on potable water lines.  They can blow up (and ruin your day.)
« Last Edit: January 14, 2022, 07:11:00 PM by KWKloeber »
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Stu Jackson

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Re: Disappearing coolant
« Reply #4 on: January 16, 2022, 10:58:05 AM »


.....................
.....................

A leaking WH (again, typically a pinhole between the potable water vessel and coolant tube) typically does NOT lose engine coolant - it GAINS engine coolant. Why?  The closed engine-coolant loop maxs out about 15 psi, and the hot water vessel is nominally at whatever pressure your potable water pump is set at (much higher than the engine pressure.)  So coolant canít push against that high pressure and get into the potable water side (good thing cuz itís toxic, so BEWARE if your potable water is unpressurized.)  The WH pressure can actually go much higher than the engine block*** (why the WH tank has a temp/pressure relief valve) so potable water can move in the opposite direction, sometimes with coolant ending up in the bilge or wherever the coolant reservoir bottle can overflow to (potable water pushes into the WH hoses, to the engine block, out the exhaust manifold pressure cap, to the coolant reservoir overflow.)

..............
..............

Quite true, Ken.

But the water heater isn't always hot, is it? 

Unless I need hot water, the electric side on my boat is off.  Indeed, I only turn the electricity to it on for about half an hour before I need it, and, when hot enough, I turn the power off.

Likewise, when I go off sailing, the water is cold when I get on the boat and only warms up when I motor.
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Stu Jackson, C34 IA Secretary, #224 1986, "Aquavite"  Cowichan Bay, BC  Maple Bay Marina  SR/FK, M25, Rocna 10 (22#) (NZ model)

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waughoo

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Re: Disappearing coolant
« Reply #5 on: January 16, 2022, 11:27:01 AM »

Once you pressurize the water system with the fresh water pump, you are likely moving water into the engine side of the circuit.  I believe that is what Ken is saying.

[Edit] assuming you have a pinhole leak in the engine coolant leak in the heat exchanger loop within the hot water tank.
« Last Edit: January 16, 2022, 11:32:10 AM by waughoo »
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Alex - Seattle, WA
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Std rig w/wing keel
Belafonte

Stu Jackson

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Re: Disappearing coolant
« Reply #6 on: January 16, 2022, 12:40:03 PM »

Once you pressurize the water system with the fresh water pump, you are likely moving water into the engine side of the circuit.  I believe that is what Ken is saying.

[Edit] assuming you have a pinhole leak in the engine coolant leak in the heat exchanger loop within the hot water tank.

Could be, Alex.  But I also open the hot water faucet if I'm not going to use the water to relieve the pressure on the (being unused) system.
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KWKloeber

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Re: Disappearing coolant
« Reply #7 on: January 16, 2022, 01:58:44 PM »

[

Quite true, Ken.

But the water heater isn't always hot, is it? 

Unless I need hot water, the electric side on my boat is off.  Indeed, I only turn the electricity to it on for about half an hour before I need it, and, when hot enough, I turn the power off.

Likewise, when I go off sailing, the water is cold when I get on the boat and only warms up when I motor.


I wasnít clear. The WH being on or off, water hot or cold, is irrelevant - the pressure pump raises the water vessel pressure to above the engine coolant pressure. Heating the water can raise it even further, but thatís also irrelevant- so long as potable system pressure is greater than 15 psi, engine coolant canít move into the WH. 

BUT as I said, if the potable pump is off, then toxic engine coolant COULD move into the potable water but itíll co-mingle/linger there until the pump is on and a tap or shower is opened up. i.e., you wonít noticeably ďloseĒ coolant, at least not a significant continuous volime because the potable system is a closed loop and thereís nowhere for the coolant to go to - unlike the engine side which is not closed and has a low-pressure relief valve.
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Twenty years from now you'll be more disappointed by the things you didn't do, than by the ones you did.
So throw off the bowlines.  Sail away from the safe harbor.  Catch the tradewinds in your sails.
Explore.  Dream.  Discover.   -Mark Twain
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