A method for sealing surgical instruments, particularly reusable electric surgical instruments sterilized using an autoclave process, includes providing at least two body shells having a runner system on the mating surfaces, aligning the body shells, securing the body shells in position relative to each other, inserting an injection device into the runner system, injecting an elastomer material from the injection device into the runner system, removing the injection device from the runner system, and curing the elastomer material. The elastomer material seals the housing chamber of the instrument. The elastomer material may bond the body shells together.