Chasing down the coolant drip

[djousset]

I apologize if this is a repeat, I have read other threads but have additional questions.

The simple question is: Is there a preferred sequence of diagnosing a coolant leak? I am having some PTSD from last year's fuel line issue and found that recommended sequences from forum members was hugely helpful.

The history: (Yanmar 2gm20f)

~Heat exchanger removed and cleaned.
~New end cap gaskets and block gasket added
~Exchanger re-installed, system flushed, new coolant added


~Engine started up and or about 10-15 minutes to open thermostat (new hot water tank and hoses has been added). Exchanger cap was off to check levels and burp any air. Coolant added to overflow.

Ran beautifully. All appeared good. Nervous captain who did the work herself became a happy, relieved captain.

Two days later I find coolant in the pan and bilge, a fair amount. Sigh. All cleaned up and new pad put down to track drips. Came back a few days later to more coolant in pan, although a small amount. Appears to be at/around/under exchanger only. End caps to exchanger are dry, hoses to and from hot water tank are dry.

Might I have tightened exchanger to the block improperly? (I alternated the bolt tightening). Do they need to be re-tightened again after it’s been run/heated up the first time? Can you over-tighten these?

I am considering adding dyed distilled water and watching for drips, is that a crazy place to start?

[GreenWave]

Are you sure your coolant cap isn't leaking? I finally traced a small slow coolant leak on my Yanmar last year to the cap. Bought a new one and all was well.

[Wolfe10]

Also look at the weep hole in the coolant water pump.


Clean the engine pan and put down some paper towels. That may help you identify the area of the leak.

[ItDepends]

Before running around changing parts or otherwise spending a lot of time and money, with a coolant leak always start by torquing down the hose clamps. Even if you KNOW they are tight, go around and tighten them ALL again... It is a frequent cause of leaks, and a very easy fix. Makes sense to be the go-to first step in a fix.

[djousset]

@GreenWave: Thx, I replaced the cap 2 yrs ago but maybe
@Wolfe10: First round of clean towels showed it at/around exchanger. Plan to do that again
@ItDepends: Thx, I did do that first thing, all hoses and end cap screws. But not the bolts holding the exchanger to the block. I don't know if that's one of those places where you need a particular torque spec.

[djousset]

And what assumptions, if any, can I make since it didn't leak while the engine was running?

[fourlyons]

I'm not familiar with the heat exchanger on your engine, but I don't think too many of them have the bolts going through the coolant chamber. In other words, loose bolts cause exhaust gas leaks, not coolant leaks. Are you sure your bolts have coolant around them?

[fourlyons]

Originally Posted by djousset

And what assumptions, if any, can I make since it didn't leak while the engine was running?

Maybe that it takes the pressure of hot coolant to push through, I assume your system has a pressure cap.
You could try taping a paper towel to the bottom of the heat exchanger and run the engine, checking it regularly, to see exactly where you are getting the leak. You could add water color dye to make it easier.

[djousset]

Finally back at the boat after a bout with covid and have a better picture of where the coolant is pooling. Last I ran the engine there were no obvious leaks while running, nor for a time after I shut down. I returned today to a fair amount of coolant in the pan and pooling as seen in the attached picture. It looks to me that it's between the oil reservoir and the top of the block? Any suggestions?

[roberttigar]

A good investment in tools is a Mityvac cooling system test kit. It lets you pressurize the system without removing anything but the cap. And it will allow you to test the cap as well. If there is a leak, it will be indicated by the pressure dropping. Apply enough pressure and you can search for coolant drips.
Model # MV4560 was about $25 a few years ago.
Bob

[djousset]

Update: Coolant leak solved. A myriad of paper strategically placed towel pieces later and the culprit was the thermostat and gasket, and the overflow tank hosing/nipple connection. All fixed. I appreciate the tips and suggestions, I learn a lot from this group!