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Was hoping someone could help.

I am loosing freshwater from my engine at a rate of about 1 gall every hour while running. The alarm sounds, but the engine never actually over heats. There is no water in the bilge, so I am assuming the water is either going out the exhaust manifold or the heat exchanger. However, the boat is in a very remote place and I can't pressure test. I was hoping to try and determine which area the leak is occurring. The interesting thing about the leak:

1. When the engine is cold and I top up the fresh water, it doesn't leak until I run the engine.

2. When the engine is hot, the engine leaks with or without running the engine.

There is no water in the oil, so head gasket has been eliminated. The engine has never actually overheated, but the engine leaking runs about 3 degrees C hotter than the other.

I would really appreciate any help.

Hank

Hank, how many hours do you have on your engines?... Do you replace the engine zincs per the manufacturer's recommendation?... When did you last descale and pressure test the heat exchanger?... If you're loosing freshwater and it's not turning up in the oil it can only go one of two places...

1. Some leakage in the external piping
2. Leakage in the heat exchanger

I would get a water leak detector kit (like this or this) that has a suitable cap for your header tank... On my DD's it's a standard (old school) GM type cap... Pressurize the system and check for external leaks... If you can add some fluorescent agent (a.k.a. dye) to the fresh water a UV light will make finding the leak a lot easier... If you don't find any leak it's time to check your heat exchanger...

One way is to dismantle it and take it to a shop that knows how to test heat exchangers under pressure... Another way is to disconnect the seawater hoses of the heat exchanger and pressurize the system with the afore mentioned kit... If the leak is in the heat exchanger the leakage will become obvious as you'll see it on the seawater side...

Thanks for the reply. I will try to find a pressure test kit locally. I have crawled around the engine for hours and see no signs of leaking, but I guess it could have been missed. The Yanmar guys over here have also suggested the exhaust manifold, but that seems unlikely considering it is still leaking even without running the engine. Anyway, thanks for the reply.
Hank

Hank
Off the top of my head I can think of three places where the coolant could exit the system without being in the bilge.
Heat Exchanger
Exhaust Manifold
Turbocharger
Everything else is raw water cooled.
One question, what kind of coolant do you use? This is a very important question.
Bill

Yes, if you have a "wet" turbo snd/or a "wet" exhaust manifold then those are additional places where you should be looking for coolant leaks...

I saw this same question on boatdiesel.com a few years ago. You can get into the archives if you are a member or put the question to the members, there is no charge for this. Good luck

Hank C wrote: ↑Sep 21st, '15, 23:51 Was hoping someone could help.

I am loosing freshwater from my engine at a rate of about 1 gall every hour while running. The alarm sounds, but the engine never actually over heats. There is no water in the bilge, so I am assuming the water is either going out the exhaust manifold or the heat exchanger. However, the boat is in a very remote place and I can't pressure test. I was hoping to try and determine which area the leak is occurring. The interesting thing about the leak:

1. When the engine is cold and I top up the fresh water, it doesn't leak until I run the engine.

2. When the engine is hot, the engine leaks with or without running the engine.

There is no water in the oil, so head gasket has been eliminated. The engine has never actually overheated, but the engine leaking runs about 3 degrees C hotter than the other.

I would really appreciate any help.

Hank

Hank, did you ever solve this issue?

Mickey

Not sure he is on here anymore. That one is from 2015.

I saw that but wanted to see if he was still around. I removed the exhaust manifold and found 1 pit on the front cylinder exhaust. I'll pressurize the manifold today and apply some heat on the pit to see if its leaking there.

As he has not been on the site for some time I’d try sending an email and PM.

I will try that. Today I pressure tested the exhaust manifold and turbo and all is good. I replaced the heat exchanger with another one I have. So don't know where else to look.

Mickey

How far below the line does it drop? If you bring it back up to the line, and run it, does it drop again by the same amount? If it is less then I would be really scratching my head, since you would think it would be the same or worse, but if it was less then I would say there is air slowly bleeding out of the system and eventually it will even out.

Do you always use the Yanmar pink juice?

Yannis wrote: ↑May 18th, '23, 00:31 Do you always use the Yanmar pink juice?

Yes sir.

Tony Meola wrote: ↑May 17th, '23, 20:34 Mickey

How far below the line does it drop? If you bring it back up to the line, and run it, does it drop again by the same amount? If it is less then I would be really scratching my head, since you would think it would be the same or worse, but if it was less then I would say there is air slowly bleeding out of the system and eventually it will even out.

Tony, last weekend I replaced the heat exchanger and topped the coolant. Had it running for about 30 minutes and left, when I came back the level was down again but a little less than before. Now that the other engine is down decided to remove and pressure test the exhaust manifold and turbo. Turbo held 30 psi for 15 minutes and manifold held 20 psi.

Maybe its air in the system but for peace of mind everything has been tested.

Installed everything back yesterday, also replaced all the hoses in the cooling system and so far so good. The level still hasn’t gone down.

Mickey

Did you isolate the problem?

Nope but it hasn't leaked.

That's good. Hopefully that has ended all the gremlins that have been popping up.

After replacing the turbo (it had a pin hole) coolant level is still going down. I'm thinking its the exhaust manifold as the coolant level only goes down after running the boat and cooling off. Bilge is completely dry.

Bilge might be dry, but if you have a leak that is hitting the hot engine it would dry up unless it was a bad leak. Check around the engine for any stains.

Any glycol solution for cooling doesn't really evap like water and there should be puddle or stains.
Isolate and pressure check cooling system as you have done. I've chased some difficult ones.

Went to the boat yesterday and removed the coolant from the engine. When I was going to open the coolant drain on the heat exchanger I was able to open it using my hand, it wasn't tightened (maybe this was the issue, but the bilge always has been dry). Went ahead and removed the coolant and flushed the engines a few times with water. Filled the engine with water and dye and ran the boat for an hour. This morning I checked the reservoir and it was down just a little bit (maybe from air getting out of the engine), so left it filled with water and dye and will run it again next weekend. I did check the engine all around 4 times with the UV light and not 1 drop of dye. Also found the raw water pump leaking so ordered a new one. I also removed the mixing elbow and everything was black so no coolant going out of the turbo like last time.

I'll run it a few times and if it coolant keeps going down I'll remove the exhaust manifold and heat exchanger to pressure test them. Also bought a combustion leak tester to test the head.

Stay tuned.

Went to the boat today and the reservoir was about 1"-1.25" low. Also the engine needed to be topped off. I haven´t started the engine since last weekend when it was a little low and I didn´t filled it back up to the "full" line.

Can this be that air is getting out of the system? Because its weird that the reservoir is lower without running the engine.

Also checked the whole engine with the UV light and nothing on the outside, even removed one of the caps of the HE to see if there was dye in the saltwater side and nothing.

Every thread on boatdiesel where coolant was lost overnight it was due to the exhaust manifold but I don't want to spend $4500 for it to not be the problem

Mickey

If you have air in the system, the reservoir will drop as the engine cools down. That would be the antifreeze being sucked back into the engine replacing the air that was pushed out. The air is only pushed out when the engine is running. I would think by now the air should be out of the system. If it wasn't, that is a lot of air and you would probably be running a little hot.

A trick mechanics use is to drill a small hole in the flange of the thermostat so that water and air can pass through while you are filling the engines. Some thermostats are made with the hole in it. It is not large enough to impact the temperature of the engine, but it helps when filling the engine until the thermostat opens. Sometimes at idle the engine does not get hot enough to open the thermostat.

I would give it one more shot and see if it final stays full.

Micky I'm not sure what the issue is here. If the engines are not overheating what I'm reading is just normal level fluctuation in the overflow tank and the expansion tank. When my 6LP's were new to me I kept peeking into the expansion tank and seeing it was a little low, trying to add coolant. Whoops, it only accepted a cup or so and then overflowed onto the engine block. I guess that level fluctuation is why its called an expansion tank. After that I changed the fluid regularly and learned to leave them alone as long as run temperatures were normal.

BTW the fluid in your overflow tank looks yellow to me. Yanmar coolant is red.

Amberjack wrote: ↑Mar 20th, '24, 13:23 Micky I'm not sure what the issue is here. If the engines are not overheating what I'm reading is just normal level fluctuation in the overflow tank and the expansion tank. When my 6LP's were new to me I kept peeking into the expansion tank and seeing it was a little low, trying to add coolant. Whoops, it only accepted a cup or so and then overflowed onto the engine block. I guess that level fluctuation is why its called an expansion tank. After that I changed the fluid regularly and learned to leave them alone as long as run temperatures were normal.

BTW the fluid in your overflow tank looks yellow to me. Yanmar coolant is red.

Level is supposed to go above the full mark when hot and when it cools down go back to the full mark. In my case, this engine only goes down after running the engine.

I use red coolant. What you see in the picture is water with dye as I was trying to see if there was any leak on the outside of the engine or in the bilge.

Ummm. I thought it was supposed to fluctuate between minimum n maximum, plus or minus a bit.

If going below minimum, refilling n going below again that’s another story.

Mickey

Sorry I don't remember if you tried changing the cap on the heat exchanger. If you haven't, I would give it a shot. Nothing to loose.

A friend of mine had the same problem with gas engines on his Sea Ray. Chased it for three years. Same route as you. Still hasn't found it and is now having another mechanic take shot at it.

Hi Tony,

Yes I did replace both caps with new ones.

Mine was evaporating from the connections in the tube from the heat exchanger to the expansion tank. Invisible to the naked eye, plus no marks in the bilge. I changed the tie wraps and the problem stopped.

Ran the engines last night at idle for about an hour and this morning there was no coolant missing. All I can think is that the drain that was hand tight was the issue. I'll run it next weekend and confirm back.

Either that or you had a big air bubble in it.

I Had this issue on my 8LV and it was a rotted out heat exchanger drain plug. Mine was made of copper and it had just deteriorated after 3yrs.
Hopefully your issue is now resolved.

If it continues, pressure test with a radiator pressure test kit before you tear it down. You can rent them from O'Rielys or other parts stores.

Did that qa long time ago and the pressure didn't drop.

Went to the boat today and coolant is low once again, about 1/2" low on the reservoir. At this point I'm going to replace the exhaust manifold. I'll keep you guys updated.

Micky

I don't get it. You say it holds pressure. But the question is how. Before you tear it down, I would pressure test it again.

I will pressure test it again next weekend.

Went to the boat today and the level was at the "full" mark like it should. Hopefully it was air in the system. Ran the engines today for 1.5 hrs until they got to temperature and will check again next weekend.

Well, level is still at full. Will run the boat next weekend and if there is no change I'll drain the water with dye and refill with coolant.

I was able to run the boat yesterday with my dad and today the coolant level is low once again, when I told him that the level was down, he said that that engine's exhaust was smoking a little bit white compared to the other one so I'm going to replace the exhaust manifold. I already have it so here we go for one last time.

I'll report back.

Frick'N boats...sometimes it never stops. You have not had an ez ride on your rebuild from the start.
BUT damn you are SOOooo close.

Just one more thing to be finally done...till the regular boat maintenance starts.


I got my fingers crossed for you Micky.

Just replaced the exhaust manifold. As you can see (red rtv) someone worked on this before.

Micky, Carl,

After all I've been through this winter (turbos, broken arch with solars, broken steering wheel and instrument panel, etc etc), I discovered too that someone at some point in the past have put their fingers in mending? servicing? testing their abilities? all of the above? trying to fix things. And when I was asked “who did this?” I couldn't provide an answer...

So many years, so many previous owners, so much history in every individual boat that we own.
And still, we spend money and abuse ourselves in trying to keep up with time.
This is who we are!

Found the pitting and water mark on the manifold, cylinder #6. Just like in the turbo.

Micky

Sorry to hear your problems have continued. Thought you had it with the last report. Hopefully this will do it and you can enjoy the fruits of your labor.

I hate when people use a quick fix to make things work, then you inherit their problem.

Tony Meola wrote: ↑May 21st, '24, 21:06 Micky

I hate when people use a quick fix to make things work, then you inherit their problem.

Reminds me of the conversation I had with the mechanic who worked for my boat's previous owner. "I was just trying to keep the old man's dream alive." After six seasons, I think that I have sorted out most of the puzzles that he left for me.

Peter

It is the same with a house. God, I hate what some people do themselves. I finally got tired of putting up with the electrical issues we had. I was always chasing something in the house. So, I just had the panel redone and the bad DIY wiring straightened out. Electricians don't come cheap either.