The decline in the fan speed and the subsequent rise in the temperature of the engine could be as a result of the belt tension. Mechanically, it can be assumed that the tension of the fan belt to its pulley has a lot to do with the engine speed. If the tension of the belt is weak it can reduce the pulley rotational speed due to the slip arising from the micro space between the belt and its pulley.
Adjusting the speed of the fan has a lot to do with experience because the practice seems simple but some difficulties could be encountered which could lead to the damage of the belt or adding an extra expansion to it. Remember that most belt adjustments are carried out the moment the belt starts expanding due to longtime usage.
STEPS IN TENSIONING OF FAN BELT
- Where the pulleys tension the belt, use two spanners to loosen the hinge fixings and slacken off the clamping bolt.
- Swing the pulley away from the engine to tension the belt. Use a wooden lever (a hammer handle will do) between the pulley and engine block to get the right tension.
- While the belt is held under tension, tighten the clamp bolt. Re-check the tension and if it is correct re-tighten the hinge fixings.
For cars or engines with split pulley adjustment, undo the nuts holding the pulley together and take off the outer half.
Remove one packing piece from the center and refit the outer half, with the displaced packing piece on the outside; re-tighten the nuts, taking care not to trap the fan belt near the hub.
With the pulley assembled, rotate the engine one revolution before checking the tension.