4HK1 diesel engine uses stainless injector sleeves in the head. In order to replace these injector sleeves with the head installed on the engine, the sleeve must be pulled out, then the new sleeve seated to prevent coolant leaks. For removal, GM-50547-3 Remover Assembly is tightened into the sleeve, and GM-50547-1 Injector Sleeve Puller Bridge is installed over GM-50547-3. The included nut is tightened against GM-50547-1 to draw GM-50547-3 and the sleeve out of the cylinder head. To install the new sleeve, the sleeve is placed into its bore, and GM-50547-2 Injector Sleeve Installer is bottomed in the sleeve. GM-50547-2 is then driven with a hammer to fully seat the new sleeve into the cylinder head. Unapproved methods may damage the sleeve, and can lead to leaking.