Automotive Systems

Formerly Automotive Systems I

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Fan And Belt

Fan and Belt

One of the easiest and quickest checks to the cooling system is the fan and fan belt. Check the fan for bent blades, cracks, and other problems. A bent or distorted fan on one with a loose blade should be replaced. Where the fan is just loose on its mounting, tightening is in order.

Fan belts, or drive belts, should be checked for wear and tension. Most wear occurs on the underside of the belt. To check a V-belt, twist the belt with your fingers. Check for small cracks, grease, glazing, and tears or splits. Small cracks will enlarge as the belt is flexed. Grease rots the rubber and makes the side slick so that the belt slips easily. A high-pitched squeal results from slippage. Large tears or splits in a belt allow it to be tossed from the pulley. On vehicles with a set of two belts, replace both if one is worn and requires replacement.

Use a belt tension gauge to check and adjust the fan belt tension. When you do not have a gauge or if space does not allow use of a gauge, you can make a quick check of belt tension. Press down on the free span of the belt, a point midway between the alternator or generator pulley and the fan pulley. Measure the amount of deflection. When free span is less than 12 inches between pulleys, belt deflection should be 1/8 to 1/4 inch. When free span is longer than 12 inches, belt deflection should be 1/4 to 1/2 inch.

A slipping belt can cause overheating and a run-down battery. These troubles result because a slipping belt cannot drive the water pump and alternator fast enough for normal operation. Sometimes a belt will slip and make noise even after it is adjusted to the proper tension. Several types of belt dressing are available which can be applied to both sides of the belt to prevent this problem. Belt dressing helps to eliminate noise and increase belt friction.

The fan belt should be checked every time a vehicle comes in for preventive maintenance (PM) to make sure it is in good condition. A fan belt that has become frayed, or has separated plies, should be replaced.

Replacement of a defective belt is usually made by loosening the alternator or generator mounting bolts. With the mounting bolts loose, push the alternator or generator closer to the engine. This action provides enough slack in the belt so it can be removed and a new one installed. After installing a new belt, adjust it to the proper tension and tighten the mounting bolts.

Published by SweetHaven Publishing Services
Based upon a text provided by the U.S. Navy

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