The listing, Prestone Stop Leak has ended.
Prestone Heavy Duty STOP LEAK.
*ACTS FAST
*FOR CARS, TRUCKS, AND TRACTORS
*SEALS - RADIATORS, HEATERS, GASKET JOINTS, HOSE CONNECTIONS.
MIXES WITH ANY ANTI-FREEZE
This is formulated for use with modern day cooling systems and is equally effective in older systems.
Just put this in your radiator when engine/coolant is cool. Replace the cap and run engine at idle with heater on until the leak stops. Simple as that!