These engines are very difficult to service and many tasks on them need specialised tools. It is therefore important that when working with timing chains, camshafts or when lifting the cylinder head it is very important to read the instructions and ensure that correct tools are used to avoid damaging the engine. The timing system is delicate, and if an error is made something really dreadful can happen to the engine; therefore, only experienced mechanics should handle such jobs, and if you are in doubt, seek advice from a specialist. Verify all tasks before commencement of the engine to avoid any form of incorrect working. Since this is an 'interference' engine design, a snapped chain damages the valves and, most likely, the pistons, which requires cylinder head extraction. First, remove the battery, take off the spark plugs and hold the number one cylinder at the Top Dead Center or TDC for short. It is followed by the elimination of valve covers and timing chain cover depending on the arrangement of timing chains in the 4.6L and 5.0L engines. For 4, 6L, you do not need the toothed wheel located in the crankshaft housing and position the crankshaft as described above, and then take off the rocker arms of the cylinders that are marked. Move on to the next step in order and uninstall the timing chain tensioners, and chains, and if need be, the camshafts. When working with 5.0L engine, a special tool needs to be used in order to rotate the crankshaft, compress the tensioners and properly and gently remove the primary timing chains and VCT assemblies so they would not be confused with one another. Inspect sprocket teeth, chains, and tensioners and replaced any that are found to be worn out or damaged. Whilst the installation for the 4.6L engine, accurately align the timing marks fitted the timing chain guides and tensioners then the rocker arms. In the course of the assembly of the 5.0L engine, make sure that the assembly marks in VCT match the secondary chains, fix the primary timing chains and ensure that all parts are well anchored. Last, turn the crankshaft to feel if there is any resistance and do it in the reverse method of its removal.
