How often should the timing belt be changed on a Movano A 2.5 CDTI?

The G9U is considered one of the more durable engines in its class, but only if its timing drive is maintained. In workshop practice, the belt is changed every 100,000-120,000 km or every 5-6 years, calculated from the actual installation date rather than the previous owner's claim. When buying a used example without documented replacement, assume the worst and change the timing kit immediately. The cost of the kit is incomparably lower than the consequences of a broken belt. The 2.5 CDTI belt has 89 teeth and measures 848 mm long and 25 mm wide. Never replace only the belt: the kit must include the idler pulley, tensioner pulley and water pump, which is driven by the same belt and can destroy the new timing drive if it fails.

What happens if the belt snaps while driving?

The engine stops immediately and cannot be restarted. A typical account is a sudden loss of power on the road, revs dropping to zero after the clutch is depressed and a locked crankshaft. Because this is an interference engine, the pistons strike the open valves. Repair requires removal of the cylinder head and replacement of the valves, and often the guides and seats as well. Incorrect installation is the second common cause of expensive failures. The timing drive cannot be fitted correctly on this engine without the proper tools: the crankshaft is locked through an opening in the block beside the oil filter, while the camshafts require a locking tool because the exhaust camshaft is loaded by the valve springs and turns by itself. A timing drive assembled "by eye" runs noisily and unevenly and can destroy the water-pump sprocket after only a few thousand kilometres.