I read your article about timing belts. I have a question. I have a ’92 Olds Eighty Eight with 109,000 miles. A few months ago my mechanic suggested that I replace the serpentine belt, which I did. Is this the same as a timing belt?

– Ruth A. Johnson,

North Augusta, S.C.

Oops! Sorry if I caused you any concern over this. A large number of vehicles use a serpentine or V-ribbed belt to drive the accessories. This belt is somewhat similar in appearance to a timing (camshaft-drive) belt, but has longitudinal ribs rather than perpendicular cogs.

Serpentine belts get their name because they snake back and forth through the pulleys, driving accessories from either the ribbed front or smooth backside of the belt.

Serpentine-belt-driven accessories might include the alternator, power steering pump, A/C compressor and, depending on the engine configuration, the water pump and air-injection pump. In the past these components were driven by perhaps three or four V-belts, which required a wide multiple-groove crankshaft pulley and slightly offset accessories. Replacing multiple belts with one long, snake-like belt saves space (which is especially important when the engine resides sideways in the chassis), reduces horsepower-robbing friction and speeds replacement.

Serpentine belts are usually held to the desired tension with a spring-loaded pulley/tensioner, making periodic adjustment unnecessary.

Serpentine belts generally offer quiet, long-lasting performance, but do require replacement when excessive cracking of the ribs or fraying is noted or embedded foreign material causes a noise complaint. Pulley misalignment also can cause squeaking, generally due to a poorly fitted accessory. One drawback to the use of a single belt is that should it fail, the vehicle is out of commission, due to the loss of all accessories. For this reason I prefer to hang on to the old serpentine belt at replacement and keep it onboard for emergencies.

Replacing a serpentine belt is quite simple, after noting its proper twists and turns around each accessory. (Check for a routing decal or draw a sketch.) Once the tensioner is drawn back, via a wrench or bar, the old belt is slipped away from the pulleys, and the replacement inserted. When the belt is removed this is a great time to wiggle the tensioner pulley and idler pulley (if used), checking for excessive looseness, and spin them, observing any roughness or noise. These parts work hard and deserve periodic attention.

Alternator belt looseness is a common situation on vehicles equipped with traditional V-belts. Chirping or squealing noises can occur, as well as a discharged battery, due to poor alternator function. With the engine off and your keys in your pocket, attempt to rotate the alternator’s pulley by hand. Use a rag to protect your hand from the pulley/fan’s sharp edges. If the pulley slips against the belt, adjustment is needed. If the pulley stubbornly refuses to spin, belt tension should be OK.

Brad Bergholdt is an automotive technology instructor at Evergreen Valley College in San Jose.

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