It used to be standard practice to just change the cambelt when it was due, but now it is accepted that a complete kit should be fitted. Why? Well, with the advent of ever more complex cambelt arrangements and the introduction of plastic idler and tensioner pulleys, and the extended replacement intervals on modern engines, it’s not only the belt that wears out. Gone are the days where all you have is a cam pulley, a crank pulley and metal tensioner, now you have various idlers, double overhead cams, one or more tensioner, etc, and if any of these parts should fail, then serious engine damage will be caused…
The plastic pulleys that are used now are very reliable, the early ones were less so! The early Vauxhall Ecotec engines had a nasty tendency to break. The bearings in the pulleys can become worn and noisy too, and if left they can seize and wear the belt to the point that it breaks.
If the water pump is driven by the cambelt, Tyrrell Autos Ltd recommends the replacement of the water pump at the same time. The reason being that if the water pump was to fail after a cambelt replacement, the same amount of work would be required again to fix this.
Timing Chain Replacement
Replacement of cambelts is a routine service item because they have a finite life. Replacement of timing chains is not a service item because they are considered to have a life as long as other major mechanical parts of the engine. The timing chain may need replacing if it becomes worn due to missed oil changes and effects the valve timing, It may be shown as an Engine Management fault usually listed as a Crankshaft/Camshaft sensor fault.