Water overflowed from heat exchanger question

[Harry P]

I have a 20 years old Yanmar 2 GMF. I just opened my heat exchanger lid and the water and anti freeze overflowed by about a cup full, the engine was cold. Is this a normal thing?

Cheers
Harry

 

[gordmac]

I wouldn't think so, something must be pressurising the system.

 

[davidwf]

Have you a calorifier? Might be its coil is leaking and letting the fresh water into the cooling water circuit.

 

[vyv_cox]

Have you a calorifier? Might be its coil is leaking and letting the fresh water into the cooling water circuit.

I had an article in PBO two years about this, on Carmel 2's boat. Heating coil had corroded internally so the coolant was being pressurised by the fresh water pump. Turn the pump off and see if it happens again.

 

[Gelfie]

Most likely O ring seals on heat exchanger are broken.

 

[vyv_cox]

Most likely O ring seals on heat exchanger are broken.

How can that be? Pressure of the coolant is anything between 4 and 12 psi, dependent upon the cap fitted. Pressure in the seawater side is nominally atmospheric, open ended system. Occasionally accumulations of salts in the manifold will increase the pressure in the seawater side but this is usually accompanied by overheating problems. The question for the OP is whether it happens when the fresh water pump is on or only after motoring, which he seems to have answered by telling us the engine was cold.

 

[Harry P]

Mmmm... I'm not too sure about this. I only know enough about the engine to change the oil, filters and impeller. Is a calorifier for heating water? If so I don't have one. Also it's the fact that it had become pressurised that surprised me. When I opened it it wasn't a spray of water like if it had been hot but rather a flow of water like putting a stone in a cup of water. I hope that made sense. It could perhaps have been pressurised when motoring and then de-pressurised when cooled? But where did the extra water come from?

 

[wiggy]

Just had exactly this, mind you it only overflowed from cap overflow at high revs, exhaust elbow very blocked forcing sea water past seals to fresh system.

 

[Mistroma]

This is normal for my Yanmar 4JH4AE because there's an expansion reservoir above the engine. If I open the cap on top of the exchanger then coolant will syphon out of the reservoir. I just pop the cap on the expansion reservoir and lift the dip leg clear of the coolant before opening the cap on the engine. Failure to do this results in loss of a little coolant.

So small coolant loss on a cold engine can be normal if there's an expansion reservoir on OPs unit.