Disconnect the negative battery cable.Remove the intake manifold/cylinder head cover (Refer to 9 - ENGINE/CYLINDER HEAD/CYLINDER HEAD COVER(S) - REMOVAL).Rocker arms and lifters must be kept in order of removal and stored in the up right position.Position the rocker arms aside. (Refer to 9 - ENGINE/CYLINDER HEAD/ROCKER ARM / ADJUSTER ASSY - REMOVAL).Install special tool VM.1072A, compression tester adaptor into the injector hole and retain with an injector hold down (2) bolt .Prepare special tool MD998772A (1) for usage by inverting the tool to cylinder head holding screws so that the thread size matches the cylinder head.Install special tool MD998772A (1) onto cylinder head and using adaptor MD998772A-15 (2), place the adaptor over the valve spring.Connect a regulated air supply (3) to VM.1072A (4), and pressurize the cylinder.Place shop towels around the working area of the cylinder head to prevent valve locks from accidently entering the engine.

Using adaptor MD998772A-15 (1), collapse the valve spring (2) and remove the locks .Remove the valve spring (2) assembly.

Remove the valve seal.Repeat this procedure for all cylinders.