Ford 2003 Mustang Workshop Manual page 1687

5. Using the special tool, compress the intake valve spring.
6. NOTE: Valve stem seals should be visually inspected if new seals are not installed.
Remove the valve spring retainer keys, the valve spring retainer, the valve spring and the valve
stem seal.
7. Using the special tool, compress the exhaust valve spring.
8. NOTE: Valve stem seals should be visually inspected if new seals are not installed.