Noise from the timing belt drive
When the timing belt drive is tensioned, not only fastening of the shafts (Figs. 4, 5 and 6) but also loosening the camshaft sprocket and the high-pressure pump sprocket (Figs. 4 and 5) are essential. Otherwise, the belt tension is not distributed over the entire belt drive.
This results in incorrect contact pressure, which makes the pulleys noisy and damages the bearings. Clear indications of this fault are marks on the back of the belt (Fig. 1), stress lines on the pulley casings (Fig. 2), or belt material deposited on the pulleys (Fig. 3).
Follow the manufacturer’s instructions when tensioning. The camshaft sprocket and the high-pressure pump sprocket must be loosened (Figs. 4 and 5) in order to distribute the tension over the entire belt drive