Coolant Conundrum

[Prairie Schooner]

We've got oddly fluctuating coolant levels and composition and I can't figure out what's going on.

The coolant level will be quite low sometimes. The only time the level drops is when the engine runs, but it isn't uniform. Sometimes the level will be fine even after running for 30-60 minutes. I refill with 50/50 coolant/water mix but the other odd thing is the coolant will be considerably watered down.

This seems to have started when we had an overheated engine event. I'd cleaned the raw water filter but forgot to re-open the seacock. About a half hour into a motor transit we noticed steam coming out of the lazarette and shut the engine down immediately. I had a laser thermometer and checked parts of the engine. Temps were as high as 220ºF. I took everything out of the lazarette, removed the two engine panels in the saloon, and let it cool off. Another thing I did, thinking the water heater was over heated, was to run the hot water tap in the galley to cycle cooler water through that. There was no liquid visible when I looked in the manifold coolant reservoir. After it cooled down (and I replaced the damaged impeller) I added more 50/50 coolant. We continued the cruise though I had to add coolant periodically. I could still see some liquid in the manifold reservoir, but it would definitely be lower.

I checked the oil dipstick and there was no sign of water/coolant. The oil level did not fluctuate. I changed the oil today and confirmed that it was just (dirty) oil.

There doesn't seem to be extra liquid in the bilge after running the engine. The bilge water that is there doesn't appear red or coolant-slimy.

I tasted the watered-down coolant in the reservoir and didn't detect salt, but I don't have especially sensitive taste buds. It did have a bitter soapy taste.

The only thing that occurs to me is there could be a breach in the water heater or heat exchanger. I observed these while the engine was running today and didn't see any drips. There is no aftertaste to the water coming out of the galley or head taps. However, since the 'event' it does seem like these spit more air with water than they used to. I haven't been able to get at the exhaust outlet to see if there's a 'coolantally' residue on the hull.

The water heater is an Isotemp 16L (4.2 gal) Thin that the POs installed in 2015. The heat exchanger is original to the boat. I did a Barnacle Buster treatment on it at the beginning of this season. The raw and coolant sides of it seemed isolated from each other.

I did discover cracks in the exhaust hose from the exhaust riser to the muffler, where they are clamped to each device. There was a slow but steady drip from those while the engine was running. But if I understand the system correctly, those aren't part of the coolant loop.

Have any of you had a similar experience? What could it be? What is some other evidence I can be looking for?

Thanks much,
Jeff

 

[Pete the Cat]

The fact that you see no drips now in the heat exchanger does not mean that it did not leak when heated---steam will go through the ends when normal drips will not--and the steam will condense quickly elsewhere and be in your bilge. The exhaust hose is part of the cooling loop, though it should not have coolant in it unless the heat exchanger was compromised. It is possible that you have a pinhole leak in your heat exchanger enabled by the over heat situation. If you have not had it tested this might be a a good time to pull it all apart and go through the system. Given what you have provided, I would pull the heat exchanger and test it and the end cap seals. i have seen the caps bent just a bit from over heating and bent in a way that leaks, but escapes the naked eye.

 

[Prairie Schooner]

The fact that you see no drips now in the heat exchanger does not mean that it did not leak when heated---steam will go through the ends when normal drips will not--and the steam will condense quickly elsewhere and be in your bilge. The exhaust hose is part of the cooling loop, though it should not have coolant in it unless the heat exchanger was compromised. It is possible that you have a pinhole leak in your heat exchanger enabled by the over heat situation. If you have not had it tested this might be a a good time to pull it all apart and go through the system. Given what you have provided, I would pull the heat exchanger and test it and the end cap seals. i have seen the caps bent just a bit from over heating and bent in a way that leaks, but escapes the naked eye.

Thanks Ray. That's helpful. I should add that the overheat was about six weeks ago and these symptoms have been observed over that time.

 

[bsangs]

As an aside, why do you use a 50/50 mix Jeff? Wondering because though I have a different engine - Yanmar 3GM30F - I use undiluted coolant. Does Universal recommend a 50/50 mix? My notes from an engine class I took a couple years ago say you normally lose about 4-to-5 ounces of coolant per season. You should have Donna taste the bilge water, to be certain it's not salty. (Though if she's anything like Kim, that will definitely not happen. ) I'd think if the drips from the exhaust cracks were settling in the bilge, that water would be salty, correct? Good luck with the diagnosis. Hope it's nothing major.

 

[Prairie Schooner]

As an aside, why do you use a 50/50 mix Jeff? Wondering because though I have a different engine - Yanmar 3GM30F - I use undiluted coolant. Does Universal recommend a 50/50 mix? My notes from an engine class I took a couple years ago say you normally lose about 4-to-5 ounces of coolant per season. You should have Donna taste the bilge water, to be certain it's not salty. (Though if she's anything like Kim, that will definitely not happen. ) I'd think if the drips from the exhaust cracks were settling in the bilge, that water would be salty, correct? Good luck with the diagnosis. Hope it's nothing major.

Well, Brian, you caught me flat footed on that one. I got my first car about fifty years ago and any specific knowledge I had about antifreeze has congealed into a very vague, "That's just what I've always done." A quick web search told me it comes either full strength or premixed. I've been purchasing what a diesel mechanic recommended for our boat and proceeded as I always had. This morning, with a panic that I'd been over-diluting I made dash to the garage which set my mind at ease.

. . .

Donna was truly aghast when I told her I'd tasted the coolant. She watches a Lot of medical shows. I'd put bilge soap in the bilge a week ago and that was still in pretty high concentrate so tasting that wouldn't have given any helpful information. It might have provided a flashback to when I was a kid and got caught swearing.

 

[bsangs]

I'm tasting bilge water all the time. Pretty sure it's helped strengthen my immunity.

 

[Prairie Schooner]

Yesterday Kismet got pulled for the season. I took photos of the exhaust port just before whirlwind Donna cleaned it off. (bless her!) It looks like there's some extra drool coming out that could be coolant mixed with exhaust water.

My working hypothesis is that the heat exchanger is the culprit here. I'd already planned to work on the exhaust system, building a bracket to support the riser. The leaky hose mentioned above as well as the hose aft of the muffler will be replaced. I think I'll take the HX to a radiator shop and have it tested. So, lazarette and engine compartment boat yoga are on the docket for me over the off-season months.

 

[Christian Williams]

For what it's worth, that photo looks typical to me.

I did discover cracks in the exhaust hose from the exhaust riser to the muffler, where they are clamped to each device. There was a slow but steady drip from those while the engine was running.

That section of exhaust hose can get pretty hot. Is it soft? (mine was.) New such hose is rock hard. Also, some installations are said to have flapper valves there to discourage siphon--such valves now considered problematical and to be removed. I just don't think that section should leak at all, either water or exhaust fumes.

 

[Prairie Schooner]

For what it's worth, that photo looks typical to me.

I did discover cracks in the exhaust hose from the exhaust riser to the muffler, where they are clamped to each device. There was a slow but steady drip from those while the engine was running.

That section of exhaust hose can get pretty hot. Is it soft? (mine was.) New such hose is rock hard. Also, some installations are said to have flapper valves there to discourage siphon--such valves now considered problematical and to be removed. I just don't think that section should leak at all, either water or exhaust fumes.

Exhaust Riser to Muffler, E35-3

Leak in hose connecting exhaust riser to muffler. Universal M-25 in 1986 Ericson 35-3.

youtube.com

You're right Christian, the hose is shot. Shame on me for not catching it sooner. We did have a mechanic remount the engine in July of 2022 and replace the manifold/riser pipe in September of that year. They didn't call out this hose then, though it must have been in rough shape. Sigh. But could this account for the loss of coolant or it getting diluted?



You've got me curious about the staining from the exhaust. I'm going to track down some older photos of that area to see how the current state compares to previous years.

 

[dhill]

Hi Jeff,

I agree with @Christian Williams that the photo of the exhaust looks typical, particularly near the end of the season.

​

I also agree with @Pete the Cat that you should check the heat exchanger, particularly if it is original to the boat. My engine started running hot a few years ago, but the coolant level in the reservoir did not change. Eventually, I discovered that the coolant was not flowing through the hose between the reservoir and the engine, so the coolant level was actually low in the engine. Now, I never trust the reservoir level and always check that the coolant is topped off in the engine directly.

I also found coolant pooling under the engine, discovered a pin hole leak in the heat exchanger by rubbing my hand along the surface of the heat exchanger, and ordered a new one from Mr. Cool. The heat exchanger was relatively inexpensive ($400) and fairly easy to install (although some boat yoga was required, at least for me since I am not tall and it was difficult for me to reach the heat exchanger and connecting hoses). I also checked the connecting hoses and replaced any that were suspect.

I use a 50/50 diesel coolant mix and it has worked well, keeping the coolant color consistent.

I hope this helps! Please let me know if you have any questions.
Dave

 

[bigd14]

What about a small leak in the exhaust manifold between the freshwater system and the exhaust? Aren’t they right next to each other in the manifold? Seems like the overheat could have damaged the manifold.