Timing belt replacement, valve timing adjustment

The timing belt replacement procedures are required not only for the replacement work itself, but also for removal and installation of the cylinder head, for which the timing belt must be removed.

Installing the timing belt logically includes adjusting the valve timing. However, to avoid misunderstanding: valve timing does not change during wear. It is adjusted only once, if the timing belt was removed beforehand.

The valve train and the crank drive operate in coordination (see the beginning of this chapter) only when the valve timing is correctly set. Incorrect valve timing leads to reduced engine power and may in extreme cases cause serious engine damage, for example, if the piston crown strikes valves that have closed at the wrong time. Valve timing adjustment differs depending on engine type.

Can this be done yourself?

A complete timing belt replacement on 5- and 6-cylinder engines is possible only with special tools. Therefore, unfortunately, this work is not suitable for home workshops.

PROCEDURE

When working on a 5-cylinder engine, to remove the timing belt, remove the front crankshaft damper and, at the end, reinstall it, which is possible only with the special extension (2079) for the torque wrench and the counterhold (2084). When only replacing the cylinder head, the belt remains installed on the crankshaft sprocket at the bottom, so no special tools are required.

When working on a 6-cylinder engine, to adjust the valve timing (required after timing belt replacement and cylinder head removal), the camshafts and crankshaft must be locked precisely at TDC (tools 3242 and 3243).

Working on a 4-cylinder engine presents no problems. No special tools are required for timing belt replacement.