For the removal and installation of VANOS units and for timing of the camshafts, particular tools and processes are required, so one must go through the entire mathematics before beginning with repairs. Opening, taking out and reassembling of camshafts or VANOS units without proper tools often causes additional damage normally resulting in situation such as bent valves due to impact with piston crowns. During the whole process of exchanging the liners, the crankshaft and camshafts should be locked against rotation with the aid of BMW special tools only. Start by turning the engine off and taking out the key, then, take off the cylinder head cover and spark plugs. Turn the crankshaft so as to align cylinder one on top dead center firing position with the cylinder 1 intake camshaft lobe facing upwards. Intake with the aid of the mirror the exhaust camshaft lobe position, then unbolt and remove the timing chain tensioner with an oil collecting pan in place to capture any dripping oil. Lift the vehicle carefully and take off the splash shield, as well as the accessory belt. Loosen the vibration damper and the crankshaft front seal, then pull out the protector plug located in the lower left of the flange of the engine bell housing and fit the crankshaft lock through the bell housing flange hole to the flywheel hole so as to lock the crankshaft at TDC. Do not use them on models with automatic transmission to prevent confusion with the flywheel bore. Slip out the vibration damper hub with the counter hold tool and throw away the hub bolt. There are plugs on the timing chain housing and by unscrewing those remove the chain guide and tensioning rail mounting bolts while there is the special tool set to lock down the camshafts. Also, unbolt and take out the intake and exhaust VANOS units, and disengage the chain with the units, and then temporarily set aside. Raise the timing chain assembly with the crankshaft sprocket out of the timing chain housing and remove the timing chain from the guide and rail assembly and fit a new timing chain as well as check the conditions of the guide rails. Position the crankshaft sprocket to the chain with tooth ends facing each other, tighten the timing chain by stretching it far away from the tDC position and then slip this assembly into the timing chain housing while holding the chain stretched. Fit the timing chain assembly, rail, and guide bolts and tighten them, and then mesh the timing chain and the oil pump chain sprockets and then slide the vibration damper hub into the crankshaft. This is then tightened to final torque on the hub using hydraulic collapse nuts and special tools while seeking assistance. Replace the crankshaft front seal and fit the VANOS units with new bolts; there are two types of VANOS units. The chain tensioner should then be fitted into position, although if the tensioner has been reused, then a new sealing O-ring should be fitted also. Last of all, undo the locking tools and rotate the engine two full times, adjust the camshaft timing if required before rebuilding the engine.