If you use a pressure radiator cap it will tell you very quickly where every weak seam, loose clamp, worn hose etc. in your heater system is.
The damage from high water jacket temperature is that the engine will ping under hard load because the water nearest the exhaust valves and spark plugs in the head will boil, and allow that area to become hot enough to detonate. A pressure cap increases the boiling point and reduces the danger proportionate to how much pressure.
