Ford 2003 Mustang Workshop Manual page 1411

11. Remove the RH valve cover.
CAUTION: Do not use metal scrapers, wire brushes, power abrasive discs or
other abrasive means to clean the sealing surfaces. These tools cause scratches
and gouges which make leak paths. Use a plastic scraping tool to remove all
traces of old sealant.
Remove and discard the gasket, clean and inspect the sealing surfaces.
12. Inspect the valve cover spark plug hole gaskets. Install new gaskets, if necessary. Make sure
the gaskets are correctly seated on the valve cover.
13. NOTE: If the valve cover is not secured within four minutes, the sealant must be removed and
the sealing area cleaned with metal surface cleaner. Allow to dry until there is no sign of
wetness, or four minutes, whichever is longer. Failure to follow this procedure can result in
future oil leakage.
Apply a bead of silicone gasket and sealant in two places where indicated.