Coolant Head Tank

Our Whitby has been repowered with a Yanmar Diesel. The installation has the standard plastic coolant expansion tank but there is also an old coolant head tank that is part of the installation. An interesting note is that the head tank is an old component with the Westerbeke logo so I am not sure when it was installed. Does anyone know the reason for the head tank? My coolant is also plumbed through a hot water heater so my current thought is that it is needed for that aspect of the installation.

You need a "head" tank if any part of the circuit is above the cooling water cap on the engine. Water will constantly drain out and cause air blockage. At some stage possibly part of the water heater circuit or a hot air blower attached to the circuit was above the filler cap. You then installed the "header tank" and put a slightly higher psi cap on the engine and the normal psi cap on the header tank.

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