The coolant pressure inside the engine block can reach 70psi at high rpm before the thermostat fully opens. This will cause a corroded frost plug to leak. The BD rear frost plug is able to be seal the leak without the need to hammer out the old frost plug. We recommend installing the rear frost plug plate when the transmission is removed. The plate can be installed with the transmission in place, however the surface finish on the back of the motor is critical and must be checked prior to use.