Under extreme stress, Subaru’s 2.0 and 2.5-litre SOHC and DOHC engines, can sometimes be prone to timing belt slippage, as the teeth on the belt jump the teeth on the tensioner. As a result, the manufacturer has developed a metal guard that sits just above the back of the belt and prevents the belt from being able to lift high enough above the teeth to make this jump.

Technicians undertaking timing belt replacement must therefore ensure that the correct distance is maintained between the back of the belt and the guard. Failure to respect this gap may result in contact between them and reduce the life of the belt.

In addition, the heat generated by this prolonged action will be transferred to the hydraulic tensioner pulley and the other rigid components in the transmission system and potentially reduce their working life also. Left unresolved, the belt would eventually fail altogether, with obvious catastrophic consequences for the engine.

In order to help technicians complete a full and successful timing belt replacement, Dayco, Europe’s largest timing belt manufacturer, has developed a specific gauge that allows them to accurately set the gap in line with the 1mm +/- 0.5mm specification provided by the vehicle manufacturer.

When the gauge, which is called the Tool 11 Ezigauge and is in effect a curved plastic spacer, is inserted between the back of the belt and the guard, it allows the technician to obtain the correct clearance between these two components, even during the tightening process once the specified timing belt tension has been set.