Mystery coolant leak

[pbyrne]

A bit of background, during the summer season I haven't normally lost any coolant and the overflow bottle level remains constant.  She goes on the hard for the winter here in Canada.  In the spring, when I get her ready for launch, I find a couple of cups of coolant in the bilge and the overflow bottle is empty.  The engine is still topped up though, and after I fill the overflow bottle and bleed the air out from the little valve on the front of the engine all is well.

However, I've spotted a wee pool of the coolant stuff port side of the engine beside the transmission, after launch and moving her into her dock.

I also spotted what looks like a 'trail' where there is a clear trace down the back of the engine underneath the heat exchanger, that lines up with the wee pool.

I've run a shop towel underneath anything I can reach and it comes back dry.

Does anyone have any idea's what might be happening in general, and where I should look?  One note is that I have replaced the coolant cap 2 years ago.

Let the guessing begin! 

[Breakin Away]

I'm 800 miles away from the boat right now, so this is off the top of my head and I haven't verified that all this is accurate:

Trace the heater hoses that carry coolant to/from the HX. If they're old, cracks can propagate under the bottom of the hose clamps, and slow leaks can travel along the bottom of the hose. If the leak is on the front of the engine, it can travel along the bottom of the hose down to the HX in back. Also check your coolant pump. If the bearing fails you can get leakage from that, and it can also travel along the bottom of the heater hose to the HX. Also check to make sure your end cap gaskets on the HX are not leaking. Finally, make sure all your petcocks are closed - the drain one on the HX as well as the air bleed near your thermostat.

[robbjd]

I experienced a small, intermittent coolant leak last season. It was traced to the small brass hose bib at the coolant caps' neck. This fitting is soldered to the neck, and due to 20+ years of vibration the soldered joint leaked. The hose attached to this bib runs up to the coolant recovery tank which is in our cockpit locker.

[Nicholia]

Mine in a similar place was due to failed hose at the Heat exchanger junction (the hose that goes forward to the water pump).

[KWKloeber]

Check hoses and hose clamps on the 3rd photo here, especially the hose between the Hx and Exhaust Manifold:

https://groups.io/g/Catalina30/wiki/9626#Coolant-flow-on-the-B-series-engines-28e-g-2C-M-35B2C-M-25XPB-shown29

[pbyrne]

Check hoses and hose clamps on the 3rd photo here, especially the hose between the Hx and Exhaust Manifold:

https://groups.io/g/Catalina30/wiki/9626#Coolant-flow-on-the-B-series-engines-28e-g-2C-M-35B2C-M-25XPB-shown29

Port Side photos?

[Ron Hill]

pby : To check a hose clamp just fold up a length of paper towel and wrap it around the end of the hose and clamp.  Then run the engine and check!!

A thought

[pbyrne]

pby : To check a hose clamp just fold up a length of paper towel and wrap it around the end of the hose and clamp.  Then run the engine and check!!

A thought

Excellent idea!  Thank you!

[KWKloeber]

Check hoses and hose clamps on the 3rd photo here, especially the hose between the Hx and Exhaust Manifold:

https://groups.io/g/Catalina30/wiki/9626#Coolant-flow-on-the-B-series-engines-28e-g-2C-M-35B2C-M-25XPB-shown29

Port Side photos?

No. The next photo.  The Port Side view doesn't show a hose between the Hx and Exhaust Manifold.

A little tough love here - do you know where those two engine parts are?  If so you can see a hose between them. If not - you NEED to learn what are the components of your engine. There's resources galore on here that call out the engine components on our engines!!

[pbyrne]

I've just discovered that mechanics use a dye that shows only to UV (blacklight) in the coolant systems of cars that it's not obvious where the leak is.

https://www.amazon.ca/Interdynamics-375CS-Radiator-Coolant-Dye/dp/B002M4E0VC/ref=asc_df_B002M4E0VC/?tag=googleshopc0c-20&linkCode=df0&hvadid=459447196707&hvpos=&hvnetw=g&hvrand=4437302755376254084&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9000660&hvtargid=pla-569461451923&psc=1

Is there any reason this would be an issue with a 35B?  I already use automotive coolant in the engine (which I've wondered if that's ok BTW).

If not this is exactly what I've been looking for.  The leak seems to have stopped....again.

[Ron Hill]

pby : Maybe all of your checking /retightening may have done the trick!!

Like I said fold up a piece of paper towel and wrap it around each of the coolant hose clamps and if it starts again it will be evident!!

A thought

[pbyrne]

pby : Maybe all of your checking /retightening may have done the trick!!

Like I said fold up a piece of paper towel and wrap it around each of the coolant hose clamps and if it starts again it will be evident!!

A thought

It might have! I have the skinned knuckles to show for it.  It I could reach it with my wrench it got a 1/4 turn.  I did do your cloth trick, and nothing yet.   I was thinking of the UV, because then when it leaks again I can nail it down once and for all.  For whatever reason the clothes haven't shown it up when it leaked.  Which I know makes no sense...

Do you think the dye will hurt anything though?  If there's anyone that can answer that question Ron.  I'm pretty sure you know how a cold fusion reactor works...

[Ron Hill]

pby : Wait and see if the leak reappears.  If it does then give the dye a try.

You have to be careful that you don't keep tightening and cut into the hose.  I always try to tighten with a nut driver or socket rather than just using a screw driver.
Also on most of my hose clamps I cut a thin piece of leather and place it as a cushion between the clamp and the hose - just so the clamp can't cut the hose.

A few thoughts.