Cooling system projects

Most car makers rely on the fanbelt to cool the engine. Although it may not drive a radiator cooling fan, on most water-cooled engines it drives the water pump; on air-cooled engines it often drives the fan that blows air through the cool- ing fins. In either instance if the belt breaks the engine overheats.

Fanbelts stretch a little in service and should be checked for damage and correct tension at each service interval. Proper tensioning is important—an over-tight belt will put too much strain on the bearings of the water pump and generator, while a loose belt will slip and in time the battery will go flat because the generator is not turning fast enough.

Methods of tensioning a slackfanbelt vary: on most engines the generator is moved away from the cylinder block to take up any slack. On a few cars, how- ever, the generator is fixed and on these a split pulley is used to adjust belt tension. Remov- ing spacers from the centre of the pulley makes the belt run nearer the edge and increases the tension. If the belt cannot be tensioned fully, it has stretched and must be renewed.

When fitting a new belt, slac- ken off all the tensioning adjustment and fit it on the pulleys by hand, taking care not to twist the belt. Once it is fitted to all pulleys, tension it as shown.

Project 1: Checking fanbelt tension

Step 1. First twist the belt and look for cracks or cuts on the vee-section that touches the pulleys. If it is damaged, fit a new belt.

2. If the belt is sound, see the car handbookfor the correct method of checking the ten- sion. If one is not mentioned press the belt firmly mid-way between the two most widely spaced pulleys; there should be about 1/2 in (12mm) deflection in the belt.

*2. If your car has an unortho dox fanbelt arranoement. as on the Peugeot 104, you must check the maker’s recom- mended tensioning system. Tension is correct when there is approximately ~in to~in (1 5mm-2Qmm) between the belts when they are squeezed together firmly.