correct name is bakers solidering fluid, you can buy at b.o.c gas outlets or usually any welders ware house & most hardewares.tip clean paint off first then heat up with iron, then apply bakers & rub with brush reapply bakers & then solider flush with plenty of water.repaint using black enamel. this applys only if rad is copper and is on main core & not on tanks.remeber clean first before heating,pleasure to help happy cruising.