Coolant Leak 3GM30f

[jpstevens]

I'd like some help from the many Yanmar experts on the forum:
I'm losing coolant; no obvious external leaks. Apart from a head gasket failure what else should I consider? The engine performed perfectly recently from Houma LA to Progreso Yucatan, mostly motor sailing.
Comments and advice much appreciated

[Greatest Lakes]

Heat exchanger leak.

[jpstevens]

Thanks Greatest Lakes, I will take a careful look at the heat exchanger end caps and the core.

[bil56]

"I'm losing coolant"

how much ?

[jpstevens]

Hi Bill

Thanks for the reply. If I fill the tank as I did on my way from Houma LA to Progreso Mexico, it seems like maybe about 24 hours motoring causes the engine to lose at least a quart of coolant. If it's important, I can test this and be more accurate.

[bil56]

no smell in the engine room?
if there is an external leak, the coolant can evaporate very quickly on a hot engine, just the smell remains, possibly a slight trace of coloring ...

[jpstevens]

Thanks again Bill, What I'll do is fill the tank and run the engine while carefully checking fo a leak, especially around the heat exchanger.

[Calif.Ted]

And your coolant recovery system (expansion overflow tank and hose) is functioning normally? Are you adding coolant to the overflow or direct to heat exchanger?

[Wolfe10]

A leak from closed cooling system to raw water in the heat exchanger will give no external sign of leak.


If you have a cooling system pressure tester, you can pressurize the closed cooling system. See if it holds pressure.


If there is a leak, it could be external (like hose or hose clamp issue), internal to the engine (like head gasket) or in the heat exchanger.


After pressurizing for a suitable period of time to allow for the leak to manifest, start the engine while someone collects the first gallon out the raw water discharge. If antifreeze in it, you will be able to smell it.