Automotive radiators are currently used near their maximum operating capabilities. New temperature and pressure demands require stronger soldered joints to prevent failures. Quantitative data demonstrate a direct relation between soldering parameters and mechanical properties.Several new solders and conventional alloys have been examined. Highest strengths are achieved with silver-bearing solders, especially at elevated temperatures. A new alloy, with 3.0-3.8 Sn, 1.2-1.5 Ag, balance Pb, showed 100% strength improvement, which should raise current reliability and make the soldered radiator viable at higher operating temperatures and pressures.