Beware of a natural tendency to rotate the timing belt tensioner on the GM 16-Valve engine in a clockwise direction, says Gates. On these models, the Allen Key must be turned in an anticlockwise direction to achieve the correct tension. Failure to do so is a common error that’s likely to lead to catastrophic engine failure.
Ensure the engine is at ambient temperature and note that ‘used new belt’ indicates the progress of the pointer during the lifetime of the belt.
It’s also worth noting:
• Rotation of the engine during this procedure is always a manual procedure and must always be in a clockwise direction
• Camshaft and crankshaft sprockets must not be rotated unless the belt is installed and tensioned
• Never re-install a used belt
Some likely causes of Synchronous Belt Drive System failure in this procedure are:
• Rotating the tensioner in the wrong direction
• Failure to rotate the engine two revolutions after setting the tension will cause the arm of the tensioner to make contact with – and damage – the ‘stop’. This is a common cause of belt failure and easily identified with a subsequent inspection of the edge of the arm.
Gates Technical Bulletin TB001 deals with this procedure in detail. It can be accessed through www.gatestechzone.com
Gates points out that over recent winters, thermostats for some Vauxhall Zafira models have featured among its top five best sellers and the supplier reminds garages that thermostat issues often emerge during the winter months, when there are heating problems inside the cabin. Signs of thermostat ageing and problems that are likely to cause thermostat failure are not always easy to spot, so where possible, a preventive maintenance approach can be the responsible attitude.
The major danger signs to look out for are:
1. If the thermostat gets stuck in the ‘open position’, there is a continuous flow of coolant into the radiator causing the engine to run cold. Overcooled engines run inefficiently, which leads to increased fuel consumption, higher emission levels and more wear to engine components in general. In addition, the car interior will not heat up properly.
2. If the thermostat gets stuck in the ‘closed position’, the circulation of the coolant is blocked, which means the coolant cannot get to the radiator to be cooled. This causes the engine to overheat.
The consequences of “open failure” may be less catastrophic than those of “closed failure” but are nevertheless undesirable for the customer.