Found Antifreeze under my engine

[sailcapt340]

2000 Hunter 340….Today I found some antifreeze under my Yanmar 3GM30F. It cleaned up with some paper towel but I can’t find the source. This same thing happened last spring and was about the same amount. It never happens during the sailing and motoring season.
The only thing I do see is that the overflow container has lost some fluid. It is always just under the Full line, today its is about 1/4” above the Low Line.
I looked for drips, signs of antifreeze stains all under and around the motor but there are none. The antifreeze level under the radiator cap is full. Checked the petcocks (2) on the sides of the motor and all are dry.
I loosen the fan belts at the end of the sailing season to lessen the tension on the alternator and impeller pump but that has different antifreeze from what I found.
It‘s puzzling to me that it only happens during the winter. This winter was very cold compared to others.
Any thoughts as to a cause. Thank you for the help.

 

[JamesG161]

do see is that the overflow container has lost some fluid

Looks like your system worked as designed.

Jim...

 

[Ralph Johnstone]

The only thing I do see is that the overflow container has lost some fluid. It is always just under the Full line, today its is about 1/4” above the Low Line.

I went nuts trying to locate my "leak" and eventually traced it back to the overflow tank where the cap sealed poorly atand allowed the leak. I guess the bottle has to vent "somewhere."

Tape paper towel tightly around the neck of the bottle and check for wetness during the winter, which hopefully is gone for now.

The leakage is caused by the engine doing the shimmy while running at idle speed when coming into the slip. I finally solved the problem by stuffing a loosley wound scouring pad into the bottle to absorb the little shock waves of AF from hitting the cap.

​

That was over 20 years ago and the pad is as solid as the day I stuffed it in there.

 

[Hello Below]

It cleaned up with some paper towel but I can’t find the source. . . .
The only thing I do see is that the overflow container has lost some fluid. It is always just under the Full line, today its is about 1/4” above the Low Line.

That is a lot of coolant that has gone missing from your expansion tank. More than I would think some paper towel would cleanup. A ballpark guess would be in the order of a quart plus. Have a look to make sure that your engine oil looks like what it should. If it only happens once a season it is going to be a tough one to resolve.

 

[jssailem]

Looking at your coolant tank. It is overfilled. The black hose serves to send the overfill (as long as the hose is not plugged) down off the engine and into your bilge.

You also have a clear hose. Where is that attached? What is flowing through the clear hose? Does it also empty into the bilge?

Your engine looks very clean. You state that what is in the bilge is coolant. Could it also be oil? Attaching the cause to a cold winter would not be my first guess. You may have had a hose break, and that could be a cause. You did not mention that in your description of the problem. Such one-time-a-year leaks can be, but not always, connected to the engine. It could be how the engine is being serviced.

You might install an overfill tank and attach it to the coolant overfill hose. Much like the coolant fill tank in your car. This can prevent the overfill from emptying into your bilge.

 

[shemandr]

Does that overfill tank have the OEM cap? Mack Boring told us unless the cap is Yanmar it is subject to leak. Mine did.

 

[sailcapt340]

The picture makes the amount look worse than it is. It needed 5 paper towels, then a couple with a cleaner to wash the area down.
I check the oil and it is clean, so no water intrusion happening.
The clear hoses you see are connected to the petcocks on each side of the engine and to allow for draining the antifreeze from the block when I change it. And they are clear and dry. And just hang off the side of the engine and would drain to the area under the engine.
I do have to much in the coolant tank and that was a surprise to me.
I have an overflow that is attached to the black hose from the coolant tank. I’m leaning towards that hose being the issue. Either clogged or cracked.

 

[sailcapt340]

Yes it is the original cap on the overflow tank. Just a snap fit type. The tank itself is clean on the outside and not showing any signs of a leak. It really could be just a pin hole leak and given time it finds its way to under the engine. What does the cap on yours look like? I didn’t get a picture of it today but will in the next few days.

 

[shemandr]

It's not my boat any longer so I can't supply a picture. Sorry.

 

[Ralph Johnstone]

What does the cap on yours look like?

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Here's a 2GM20F overflow tank stuffed with a plastic scrub pad and the rubber hose protected by a split loom conduit. Cap snaps on.

 

[sailcapt340]

Same one as mine. Slides on a bracket fixed above the engine. I took it out this morning and flipped it over, thinking it may be cracked but it’s not.
I don’t have the scrub pad inside or the conduit covering the hose. I’m leaning towards the cap and hose being the issue.

 

[Rich Stidger]

I have the same antifreeze leak only over the winter. I have changed hoses, examined all possible leak points, tried to find wet spots on the engine that could be the leak source, ALL TO NO AVAIL! The engine is a Volvo MD22L-B; different from @sailcapt340 .

I have been chasing this leak for over 20 years. I have all but given up, and now I usually empty the overflow tank before winter storage. I think that seems to stop the leak, but I would have to scrub my records to be sure.

My overflow tank does have an overflow tube to the sump, but the tank is never filled and the tank is empty in the spring. So the overflow to the sump cannot be the source of the leak. The bottom of the overflow tank connects to a tube that goes to the radiator cap. So apparently the leak pulls a vacuum on the overflow tank and the leak continues until the tank is empty. Once empty, no more antifreeze appears to flow into the sump.

That's my 2 cents. I'm watching this thread, but I have bigger fish to fry.

 

[Clutch Cargo]

I the 5 years I have owned my boat, I have always found a little antifreeze underneath when checking her on the hard. I can usually clean it up with a paper towel. Drove me nuts until I spoke with a diesel tech whom I trust. He says that it is due to the cold and it is weeping out of a bolt or whatnot. Stops as soon as it gets warm.

 

[sailcapt340]

I didn’t know other people had this issue as well. Very interesting reading as you all described your findings. Almost the same to each account. When I opened my radiator cap and saw it was overfilled my first thought was a vacuum effect was happening. Some sort of scientific thing going on.
Don’t get me wrong, I’m not glad others have this issue or any issue for that matter on their boats, but I am somewhat relieved.
I will be changing out my hosing from the radiator cap to the overflow tank and adding the protective conduit covering also. My hose does lie across the top of the engine.
And during the winter layover I plan on placing one those absorbent spill pillows under the engine to catch the antifreeze that does happen, to make the clean up a lot easier.
Thank you all.

 

[Rich Stidger]

<snip>
And during the winter layover I plan on placing one those absorbent spill pillows under the engine to catch the antifreeze that does happen, to make the clean up a lot easier.
Thank you all.

The regular oil-absorb sheets won't soak up water or antifreeze. Cleanup will not improve.

 

[sailcapt340]

Rich, I defer to your expertise and won’t try to reinvent the wheel. It really is an annoying issue to have to deal with.

 

[Ralph Johnstone]

Try the poly scrub pad wave breaker in the overflow tank as mentioned in post #3. You can always give the other three to your wife as a spontaneous gift to show your affection and then duck.

 

[sailcapt340]

Sorry, I forgot to mention that as well. I plan to get some today. I think I will just leave the extra under the sink and let her find them for herself.

 

[marcham]

This is almost impossible to diagnose remotely. During normal use, you probably don't notice the very small leak at the end of the day because the heat of the block causes it to evaporate. You will likely have to do a sea trial and have someone look over the engine (you'll need a small mirror) while it's running.

The coolant level in the tank is fine .... it just drains down from the expansion tank when you remove the cap. Do you have the OEM coolant tank pressure cap (not the expansion tank, the actual metal tank) ? Some aftermarket (ebay / Amazon) may not function properly and could lead to problems.

Have you checked the bottom of the water pump with a mirror?

What type of coolant is that (it should not be green)? Normally it would be orange/red if using the approved coolant types. Usually green coolant has silicates. Yanmar specifies a silicate and phosphate free coolant type. I find the Yanmar coolant is offered at a reasonable price. Otherwise, the Delo ELC is available almost everywhere. With the mix of metals in the our engines, having the right coolant is very important. Silicate drop-out could cause some serious problems / overheating.

When the water pump seal goes, it will drip VERY slowly. The pump is rebuildable.

Most engine bilges are slightly sloped. Clean up all the coolant, then put paper towels everywhere. Check it daily. The highest point with drips is where you need to start looking.

 

[High Current]

Ha, I had a similar issue this year. Visited the boat in March and found a sizable pool of green antifreeze in the bilge.

Long story short I found a loose hose clamp behind my alternator bracket. Last thing I did before I closed up the boat was re-tension the alternator. Hmm…

I was lucky: there was an obvious bead of antifreeze about to drip from near where it was leaking which made it easy to track down.

Also worthy of note: on my Universal M25XP, the exhaust flange also seals the coolant reservoir…