[Uhehner]

I think all of the above information is correct. I might add that the heat ex-changer cap must seal to the tank.  It must not be a vented cap. The cap should have an 8- 15 lb pressure rating and bleed excess coolant to the overflow tank via a hose from the top of the HE tank to the bottom of the OF tank when the engine is hot and the coolant expands.  The heat ex-changer tanks on all my Crusader engines were always full to the top when I removed the cap when cold. The coolant level in the over flow expansion tank goes up and down depending on engine temperature. You never need to remove the heat ex-changer cap, just add coolant to the overflow tank as needed. The overflow tank cap is vented and does not seal to the plastic tank.  If the coolant level is always low in the HE when cold, I suspect you have a bad pressure cap.  Capt.  George