A serpentine belt on a Volvo 850 is one belt that runs the whole pulley system. The serpentine belt operates everything on the front of the engine from the alternator to the crankshaft. The serpentine belt is located in the front of the engine. Serpentine belts have to be replaced as recommended by the car manufacturer. Most serpentine belt specs are that if the belt has more cracks per square inch than the belt has ribs across then it is time to change the belt. In other words, if you have a serpentine belt with six ribs and there are eight cracks in one square inch on the belt, then it is time to replace the belt.
Pop the hood and locate the serpentine belt tensioner on the engine. The belt tensioner is located on the very front of the engine near the bottom. The serpentine belt tensioner will be holding the tension of the serpentine belt that is running across all of the pulleys on the front of the engine.
Put a 6mm socket onto the ratchet and reach down from the top to put the ratchet onto the belt tensioner. If you cant reach the belt tensioner with the ratchet and socket from the top, try going at it from the bottom of the engine.
Put the socket onto the bolt in the center of the belt tensioner. Then gently pull the ratchet towards the front of the car. This will release the tension from the belt. If you need to use both hands, slide the Allen wrench inside of the hole that is located beside the nut on the center of the belt tensioner. Then push the Allen wrench all the way through the hole. This will keep the belt tensioner from moving so that you can use both hands to remove and replace the serpentine belt.
Slide the belt off of the belt tensioner and off of the pulleys.
