7. Turbocharger (turbo diesel and ECO diesel only)

The turbocharger is shown in Fig. 7-1. The small-diameter turbine and impeller rotate at over 100,000 rpm. The shaft turns in floating bearings, pressure-lubricated by engine oil. Maximum turbocharger pressure (boost) is regulated by the waste-gate, which vents excess (overpressured) intake air directly to the exhaust system. As an additional safety feature, the intake manifold is fitted with a blow-off valve which also opens to limit intake air pressure.

Fig. 7-1.

Cutaway view of turbocharger. Notice bearings with multiple oil holes, and pressurized oil supply line. Faulty turbocharger is replaced as a unit; waste-gate is press-fit and not available separately.

The turbocharger/wastegate unit and the blow-off valve are mechanically simple systems which should be maintenance-free. The turbocharger operates at high temperature, and it is important that the oil surrounding its bearings be of the correct type and quality. Any failure of the turbocharger will most likely be caused by either a lubrication problem or a boost control problem. For repair, the entire turbocharger assembly is replaced as a unit. Remanufactured turbochargers are available from an authorized Volkswagen dealer at lower cost than a new part, and the old unit can usually be exchanged for partial credit.

The high operating temperature and high rotating speed of the turbocharger make extra caution necessary during repairs.