Losing Coolant: advice requested.

[edguy3]

Here's the situation on my 4JH2E in my Hunter 40.5:

Last season:

• Broke V belt, twice, overheated, but turned off immediately after alarm sounded.
• Fixed pulley alignment issue.
• Finished season without issue, including some long full day motoring.

This year:

• On launching, all looked good until about an hour later while picking up the mooring. Overheat alarm.
• Freshwater coolant is losing about 1 quart every 15 minutes and after about 45 minutes it overheats.
• Put a loopback on the hotwater heater to isolate the engine. It still leaks.
• Pressure test (in isolated mode) shows that it is losing pressure. Can hear air/water flow in exhaust.
• I can see the fresh water level decrease after filling.

I replaced the heat exchanger and the problem did not go away.
Further reading in ssca and in a sister forum ( and many others) led me to realize that:

• I left the 'Peace sign gasket" ( O ring with a chord) off because I did not remove one. While this probably affects performance, it appear to only isolate the input from the output.
• There are periodic surges of pressure in the fresh water tank. ( "Scuba Like" per forum)
• Upon starting the engine after the pressure test, it was difficult to turn over.
• Exhaust had a bit of white/grey smoke, but not obviously water vapor.

My next step is to do a compression test, but, I'm looking for advice specifically on the following:

• Does the presence of surges in the fresh water tank indicate a head crack or head gasket leak? (if not, what is it from ?)
• There is a reference to an issue with the mixing elbow. I can't see how this can be related. Am I missing something?
• Is my conclusion regarding the 'Peace sign gasket' well founded?

And of course, any other suggestions, ideas, prayers, etc.

Thanks!
/ed

 

[berner73]

Who winterized your engine?

 

[jdhohmann]

I would do a quick oil level check and see if you see any bubbles on your dip stick, or maybe even an oil change. Any bubbles is an indication that your head gasket is probably blown and leaking into your oil.
The surging might just be from your coolant getting too hot and overflowing into your coolant resevoir...
Good luck!!

 

[edguy3]

I would do a quick oil level check and see if you see any bubbles on your dip stick, or maybe even an oil change. Any bubbles is an indication that your head gasket is probably blown and leaking into your oil.
The surging might just be from your coolant getting too hot and overflowing into your coolant resevoir...
Good luck!!

I winterized the engine...perhaps not well enough. and it was DARN COLD this year. ( I did lose a battery. )

Oh, yes and the oil is clean, recently changed, and undisturbed.

 

[berner73]

Do you notice the loss when starting the engine cold (thermostat closed) or only after the engine is to temp?

1 qt/10 minutes is a lot and would expect the exhaust to be symptomatic as more white smoke than you indicate.

 

[edguy3]

Do you notice the loss when starting the engine cold (thermostat closed) or only after the engine is to temp?

1 qt/10 minutes is a lot and would expect the exhaust to be symptomatic as more white smoke than you indicate.

loss is both hot and cold. I also saw it during pressure test which was run dead cold.

thanks
/ed

 

[Don Lucas]

since the amount of water loss is so high I would think it would show in the exhaust pretty well, and it is was a head gasket that allowed water into the cylinders that it would leak when the engine was off and show up it the oil

Sounds to me that you have just some old fashioned leak, but I would think you could see that and that water would be collecting under the engine (is it)

in the end there are only few places for the fresh water to go:
1 - leak into the bilge (have you checked the various freshwater drains to see if they are leaking)
2- leak into the engine
3 - leak into the seawater outlet

BTW - I think that peace sign gasket would only affect temperature and that the surging in the tank (heat exchanger ????) is the thermostat opening and closing

 

[propellanttech]

I have to admit, I'm not knowledgeable about the Yanmar, but......

I would suspect the heat exchanger. This is an area, that you could get coolant leaking out, and it would be hard to see. Since this water is injected into the exhaust afterwards, you may possibly smell the antifreeze (if used during troubleshooting, and running the engine) but if just using fresh water to find the problem, you may not smell it. I know you replaced it already, but it is still the common element that would be hard to see if it is causing problems. I think there is a sealing issue, more than the exchanger itself.

This is just my two cents, and I'm not a paid expert to troubleshoot problems over the internet. Should I be wrong, I can not be held liable.

James L.

 

[splax]

Losing Coolant explored

While I am not specifically familiar with your engine and boat, my immediate thought was that the head gasket is allowing coolant into the exhaust through the exhaust manifold. You would smell anti-freeze while running the engine. Those surges in the coolant tank would be exhaust gases coming back from the manifold.
I considered that the engine might be damaged from something you didn't drain completely. It froze and cracked that something.
Yet another possibility for your immense coolant loss is that a drain was not completely closed after you drained the system and that your leak is from this oversight.
It could be a combination of causes making it harder to find what to correct.

Good Luck !

 

[Sailgunner]

Check the jacket the heat exchanger goes in. Mine had a pin hole leak where the water inters the mixing elbow. My mechanic said this is very common on this engine.

 

[edguy3]

Check the jacket the heat exchanger goes in. Mine had a pin hole leak where the water inters the mixing elbow. My mechanic said this is very common on this engine.

isnt that a raw water inlet?

 

[edguy3]

Thank you all!

Unfortunately, Ive been called out of town for a couple days.. so the wrenching will need to wait...

 

[kloudie1]

The big fat O-rings that seal the fresh side of the tube bundle from the sea water side would be a suspect area.. The missing peace sign gasket probably will allow overheat at higher loads, but at low load and idle it should have no effect. That is a big leak and probably is a leak between the fresh water side and the exhaust side in the exhaust manifold/heat exchanger housing. A head gasket problem with a leak that size would probably hydraulically lock the engine and would show up in the oil. I would think next step would be to pull the exhaust manifold and pressure check it off the engine where ya can see what is going on.

 

[edguy3]

Found it!

Found the leak in the heat exchanger.

See the attached photos.

 

[splax]

Congratulations! So the leak in the heat exchanger was putting the coolant into the exhaust, but not through the exhaust manifold? What a relief to know your engine is OK, just some repair on the coolant system.

 

[edguy3]

All is back together and appears to be running well. My wallet, on the other hand, is a bit lighter.

One important thing to note on the replacement parts: The replacement heat exchanger required an additional plug as it had a threaded hole that I assume was for a turbo charger. On the original unit, the casting had a place for this attachment, but, it was not machined out. I expected the casting to come with this plug.. it may have been an oversight.

I installed a new heat exchanger and new core. The old core is fine.. I'll hold on to it until I find a buyer. ( Used heat exchanger core for sale.) This will save someone a bundle when they need one.