That is the reason I run my radiator with a 0 psig cap. My donut core is a fragile thing and I do not want to over stress the cooling system. I tried to find a local radiator shop that would repair that heater core and no joy. Most would just laugh when they saw it due to it's reputation. It has been several years (10-12) since I rebuilt that heater with a re-worked core from Maine Radiator who did an excellent job. No more steamed wind shields.
