John,
Sounds like your 4.108 is the same as mine. The unit is a combo header tank and h/x, mounted on the port side of the engine right? If so, it's likely a Bowman h/x (model PE 180).
According to the Bowman folks, their units are not equipped with sacrificial anodes. Don't mistake the drain plug at the aft end of the unit for the anode -- if you do, you'll have a bilge full of antifreeze (don't ask me how I know...)
I'll try to shoot you an engineering diagram of the h/x.
Por Fin