3 cyl yanmar loosing coolant

[FB111A]

After sitting on the hard for 6 weeks we splashed today and after running the diesel for 10 minutes I had lots of AF coolant in the bilge. No sign of spraying about. I shut it down and found the expansion tank empty. Exhaust and raw water flow seemed normal. It had previously been leaking down a few ounces over several engine hours. Where to start looking?

 

[jibes138]

The hot water heater is on that circuit, see if that is leaking.

 

[Ralph Johnstone]

Where to start looking?

Tough one if it's appearing in the bilge and not just vanishing into thin air. Assuming it's coming from the engine itself:

Vacuum breaker.
Drain cocks.
Radiator cap.
Hose connection (only when hot).
Sea water pump shaft seal.

 

[Benny17441]

Don't forget the pump itself. Check the weep hole and if it shows any leaking coolant replace.

 

[FB111A]

Thanks all, I'll start chasing those things down Sunday or Monday.

 

[Siamese]

Obviously, there are plenty of places it could be leaking. Maybe you'll be lucky like I was. My leak, that was emptying my overflow tank, was right at the top of my engine where the soft rubber tube from the overflow tube connects. There was no clamp there, so I installed one stainless steel mini clamp and problem was solved.

 

[Ron20324]

... My leak, that was emptying my overflow tank, was right at the top of my engine where the soft rubber tube from the overflow tube connects. There was no clamp there, so I installed one stainless steel mini clamp and problem was solved.

The same place, similar problem. There was a small clamp that had been tighened down until it hit the tank and was prevented from being totally tightened. Loosened it, rotated it some, tightened down, problem solved.

 

[FB111A]

Leak. DUH!

As one of the posters said check simple stuff first. Engine block drain: check
Fill cap on heat ex: loose
That was easy. That is why the remote expansion tank was empty , it is higher than the heat ex fill( so its height matches the hot water tank) and why all the spilled coolant was under the engine. Thanks all for the suggestions.

 

[PGIJon]

I had a coolant leak under the sole in the coolant lines that went to the water heater. Here are 2 discussion on it: http://forums.hunter.sailboatowners.com/showthread.php?t=173773 and http://forums.hunter.sailboatowners.com/showthread.php?t=173808

-Jon

 

[MitchM]

you can check for a coolant leak without powering your engine on and risking damage . get a STANT tester which pressurizes your system by attaching in place of the radiator cap. pressurize to about 7 PSI and start checking for coolant leaks at every fitting with a white rag which will show the green coolant. in my case, there was a pinhole leak in the bottom of a hose to the hot water heater , off the engine block . the hose had abraded on the bulkhead. the leak was dripping on the hidden side of the bulkhead between engine and hot water heater into the bilge. i was losing 1/2 the overflow tank per trip. wrapping that hose then replacing it solved the problem. On yours, I'd check every connection and fitting between your radiator and your heat exchanger, including all the heater hoses.

 

[SEMPERAVANTI41]

You can use a "leak detection dye" such as: http://www.amazon.com/Interdynamics-375CS-Radiator-Coolant-Dye/dp/B002M4E0VC