Yanmar losing coolant

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Tim R.

Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
Here is what I know:

Engine is a 14 year old Yanmar 4JH2E with 2000 hrs.

- Earlier in the season the engine would use a few ounces of coolant when I ran it about an hour or 2
- Now suddenly the coolant is disappearing at the rate of appr 64 ounces per hour
- No sign of coolant in the oil.
- No sign of oil in the coolant.
- No sign of coolant in the bilges or under the engine.
- Engine otherwise runs perfectly. Good power and smooth operation. Starts on first try.

Last night I performed some diagnostics with a pressure tester. Here are the results:
- Engine off, system pressurized to 16lbs, tester slowly lost pressure. Started the engine and AF came out the exhaust. Took a few tries to start.

- Refilled system, connected tester, started engine. No jump on the tester. If the gauge suddenly jumped up it could indicate a head gasket problem.

- Engine running, pressurized the system to 16lbs and needle did not jump around. If it did it could indicate cracked head or block. System slowly lost pressure.

I am thinking bad heat exchanger. I will pull it tonight to check.

edited to add statement about coolant in the bilges.
 
Rick D

Rick D

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Jun 14, 2008
7,204
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Do you have a water heater hooked into the fresh water side? Is it in a compartment that drains into the bilge? I have had some leakage before I traced to the heat exchanger coupling in the hot water heater. Just a thought.
 
sailaway78

sailaway78

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May 11, 2005
3,431
Seidelman S37 Slidell, La.
Look at the heat exchanger

First place to look, from the symptoms you describe is the heat exchanger. There are very few places for the raw water and anti freeze to get mixed together. Heat exchanger is the most likely suspect here.
 
Tim R.

Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
Thanks Rick, I do have a water heater(2 years old), but that would not explain the coolant in the exhaust. No evidence of coolant in the bilge.
 
Rick D

Rick D

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Jun 14, 2008
7,204
Hunter Legend 40.5 Shoreline Marina Long Beach CA
Missed that. Yea, that sounds like the exchanger.
 
tkanzler

tkanzler

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Sep 5, 2007
689
MacGregor 26X Rochester
Tim R. said:
- Engine otherwise runs perfectly. Good power and smooth operation. Starts on first try.
<snip>
- Engine off, system pressurized to 16lbs, tester slowly lost pressure. Started the engine and AF came out the exhaust. Took a few tries to start.
Click to expand
My first impression is a leaking HE, but the 'few tries to start' line makes me think otherwise.

If the muffler has a drain, then drain it and pressurize the coolant as you did before. Give it some time and see if it's coming out the drain.

But that starting reluctance has me wondering.
 
kloudie1

kloudie1

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Nov 6, 2006
10,220
Hunter 34 Mandeville Louisiana
Sounds mostly like a heatex problem except for the part about the coolant in the exhaust... Do a quick warm torque-tighten on the head .. then pull the exchanger tube bundle and look at it for pinholes.. or a bad gasket on the ends. Hope ya find it, Tim
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,362
Catalina 34 224 Maple Bay, BC, Canada
kloudie1 said:
Sounds mostly like a heatex problem except for the part about the coolant in the exhaust...
Click to expand
Tim, wouldn't it be more like this?

Sounds mostly like a heatex problem BECAUSE OF the part about the coolant in the exhaust...

FWIW, our 1986 HX was replaced with a larger 3 inch HX in 2003. It was still working, but I installed the larger one to avoid overheating our M25 at high revs. Couldn't tell you the condition of the old one, but I'm guessing that at its age it was starting to near the end of its useful life, engineering-speak-wise.
 
kloudie1

kloudie1

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Nov 6, 2006
10,220
Hunter 34 Mandeville Louisiana
Ya right, Stu.. I was thinking "no connection between combustion side and leaky heatex".. but on shutdown and pressurization, the coolant from the heatex would go to raw water side and exit the exhaust. ..
 
Tim R.

Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
I am presuming that when I pressurized the system, the coolant entered the raw water side and back filled one of the cylinders that had it's exhaust valve open. This would explain the hard starting.

I removed the HE tonight and it looks like new. No visible signs of leaks but I will have it pressure tested tomorrow. The exhaust housing also looks very clean. It may be possible that the O-rings are failing and allowing the AF to enter the raw water side of the HE.
 
Stu Jackson

Stu Jackson

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Feb 26, 2004
23,362
Catalina 34 224 Maple Bay, BC, Canada
Tim, could be in one of the tubes, you'd never see it. Since you use the boat so often, the inside's gonna look clean, mine always does. I doubt if the O rigns have anything to do with it, 'cuz the tubes carry the coolant and the shell is the raw water. 'Cuz if it wasn't, when you replaced the zinc something other than seawater would dribble out.

Good luck.

Stu
 
Tim R.

Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
Stu, the design of the Yanmar HE is very different from the Universal. The HE core fits inside the exhaust manifold and uses O-rings to isolate the fresh water circuit from the raw water.

 
woodster

woodster

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Sep 15, 2009
6,244
S2 9.2a Fairhope Al
there is also a gasket at each end of the heat exchanger ...round in shape and has a devider that crosses the tubes ....i call that the peace sign gasket.....lol and it may be off its location some on the ends or broken...that would be letting the anti f leak into the raw water side...

regards

woody
 
Maine Sail

Maine Sail

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Feb 6, 1998
11,760
Canadian Sailcraft 36T Casco Bay, ME
Tim R. said:
I am presuming that when I pressurized the system, the coolant entered the raw water side and back filled one of the cylinders that had it's exhaust valve open. This would explain the hard starting.
Click to expand
In order for that to happen you would have ideally needed to fill the entire wet exhaust enough to back fill all the way into the cylinders. That AF/water mix would have entered the exhaust at the injection point and had to fill the water lift and hose all the way back to the elbow... I will be curious to see how the HX pressure tests. It would likely take gallons of leakage to do that..Also if the seacock is open pushing the RW mix past the impeller vanes is also an easy path for the pressure to escape..

Crossing my fingers it is an o-ring issue or HX...
 
Tim R.

Tim R.

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May 27, 2004
3,626
Caliber 40 Long Range Cruiser Portland, Maine
Maine Sail said:
In order for that to happen you would have ideally needed to fill the entire wet exhaust enough to back fill all the way into the cylinders. That AF/water mix would have entered the exhaust at the injection point and had to fill the water lift and hose all the way back to the elbow... I will be curious to see how the HX pressure tests. It would likely take gallons of leakage to do that..Also if the seacock is open pushing the RW mix past the impeller vanes is also an easy path for the pressure to escape..

Crossing my fingers it is an o-ring issue or HX...
Click to expand
Maybe not. The mixing elbow on this engine is high and the port going into the exhaust manifold is lower than the port exiting to the muffler. I think it could leak back in without filling the hose and muffler.

Paul at Portland Radiator should be able to test the HE core this afternoon or tomorrow morning. I am going to get some new O-rings and reassemble and test.

The inside of the HE housing/exhaust manifold look great. No signs of corrosion.
 
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