Strange coolant leak

Mark26

Mark26

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I originally posted the notes below at the bottom of my “At last” post, but thought it might be good to repost them here under a different title.
 
I have a mysterious antifreeze leak which I need to fix.

My antifreeze leak has been going on for a few years and I haven’t managed to find the source. It doesn’t leak a drop all summer or autumn, it only leaks when the temperature falls below 5C.

My diagnosis is there must be a join, possibly between dissimilar metals, where one side is contracting when cold allowing the leak. I’ve been all over the engine and hoses checking all nuts, clips etc are tight and have run fingers and tissue paper over every join and gasket but have found nothing.

I did it this winter when it started leaking around late November when the temperature dropped, and found nothing.
And I did it the winter before and found nothing.
And the winter before that.

I have pumped many litres - I’d guess maybe 10 litres in total over a few years out of the bilges which are otherwise completely dry. It’s definitely antifreeze, and yet the strange thing is I’ve never had to top it up! The coolant temperature continues to be normal and the coolant reservoir is ok. It’s gone down a little, but nothing like the amount I’ve pumped out.

I’ve decided the antifreeze I’m pumping out looks rather thin, suggesting I may be leaking antifreeze and water separately which are mixing in the bilge. This points me towards the join between the coolant pipes and the calorifier. I have felt around them for wetness before, but it occurred to me that I’ve never actually put a spanner on them to see if they will pinch up, and it could explain both fresh water and a little antifreeze to colour it.

Hence I shall be hanging upside down with spanner in hand tomorrow.

Its not a major problem, in fact not a problem at all during the season as it doesn’t leak a drop from March to October, barring the odd very cold night, but I’d be very happy to cure it once and for all.
 
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Well that failed.
Four years I’ve been trying to find the source of this leak and work out why I’m lifting lots of antifreeze mixture from the bilges whilst not having to top it up.
I’ve still drawn a blank.
I’ve been over every inch of the engine and traced all coolant pipes and water pipes and can’t find any sign of seepage, yet still I get puddles under the engine every winter.

The puddle forms under the engine and is retrained there by a hull stringer. It’s not from the calorifier as that sits over a different hull section and any water coming from it would fall and sit in a different place. The same is true of my stern gland, which is a Volvo drippless type and doesn’t leak, and if it did any leaks would fall in a different place and be retained there.

I’m getting antifreeze puddles under the engine, which can only come from the engine, which only happens when the temperature is below 5C, doesn’t leak a drop all summer, and the antifreeze has never, in four years, needed topping up in spite of me removing 2 litre puddles of it twice a year for 4 years.

I remain perplexed but unworried.
 
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Just a few thoughts, maybe It’s not leaking antifreeze, is there a thin layer of previously spilt antifreeze in the bilge that has now dried and you cannot see it. Fresh water leak mixes with layer of antifreeze?
I would get some talcum powder and sprinkle it around the engine and bilge, you will then get some tell tale marks that you can trace the leak. I had similar, turned out to be a tiny leak from the front shower dribbling to the rear of the boat.
 
Bran said:
Just a few thoughts, maybe It’s not leaking antifreeze, is there a thin layer of previously spilt antifreeze in the bilge that has now dried and you cannot see it. Fresh water leak mixes with layer of antifreeze?
I would get some talcum powder and sprinkle it around the engine and bilge, you will then get some tell tale marks that you can trace the leak. I had similar, turned out to be a tiny leak from the front shower dribbling to the rear of the boat.
Click to expand...

Thanks for the suggestion Bran,
after each oil change, when I regularly end up sloping oil from the filter into the same hull section under the engine, I always clean up with a very strong bilge cleaner which leaves it looking like you could eat your dinner of it.

Although I say the leaked liquid lifted from the floor looks like weak antifreeze, it is just a bit weaker looking than I’d expect as opposed to tainted water. I tested the antifreeze in the expansion bottle and it was good for -30C and looks as one would expect.

I recently watched a plumbing video where they said water is at its most dense at +4C then between +4C and 0C it expands. I didn’t know that. I thought it only expanded when it froze. Those expansion temperatures are exactly when mine leaks. Something somewhere is being forced apart.

The sprinkling of talc is a good idea. Thank you.

I shall have to try looking for it when temps are in the leaky zone, instead of going down there and looking after the event.
 
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I have exactly the same problem !
Been slowly leaking anti freeze all winter - can't tell from where.

Took her out yesterday to run the engines up to temperature and - the leak has stopped !!
 
I wonder if it is a leaky core plug.

It seems that both the pressed type and the threaded types are prone to leakage.


Of course it's worth bearing in mind that once the engine is up to temperature a very small leak will stop because the liquid is vapourised by the hot engine. This would be especially likely if it was a core plug problem i.e. on a hot part of the engine.
 
Mark26 said:
I tested the antifreeze in the expansion bottle and it was good for -30C and looks as one would expect.
Click to expand...
Out of interest, have you tested the liquid under the engine? Might help in working out if it's pure coolant or not, which might be a clue as to the source?
 
KevinV said:
Out of interest, have you tested the liquid under the engine? Might help in working out if it's pure coolant or not, which might be a clue as to the source?
Click to expand...

i haven’t tested it, but it is definitely coolant. It can only be one of four things: fuel, oil, water, or coolant, and is definitely the later. I have the Volvo green antifreeze in mine which is what ends up on the floor pan.
 
Interesting that other Volvos do the same. I am relived to know there is nothing drastic wrong with mine, and there are others which do the same, so thank you for that.

Maybe at some point, a Volvo expert will come forward and let us all know exactly what it is.

Thank you all again for the input.
Mark.
 
Mark26 said:
i haven’t tested it, but it is definitely coolant. It can only be one of four things: fuel, oil, water, or coolant, and is definitely the later. I have the Volvo green antifreeze in mine which is what ends up on the floor pan.
Click to expand...
I meant testing its concentration - it would give you an idea of how much you are actually losing. Some dyes are incredibly pervasive, so a little looks like a lot.
 
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