The serpentine belt on a 2003 Chevrolet Silverado runs the entire pulley system on the front part of the engine. Older model Chevrolet Silverado trucks had three different belts to run each pulley. Replacing the serpentine belt on the 2003 Silverado is a job you can do yourself in just a matter of minutes. A serpentine belt needs to be replaced whenever there are more cracks in a square inch area then there are ribs across the belt.
Pop the hood and locate the serpentine belt routing diagram located on the top of the fan shroud. If the diagram is not there, tale a notepad and draw out the exact belt routing over the pulleys before you remove the old belt.
Locate the belt tensioner, which is at the top left above the air conditioner compressor. Find the proper socket that fits the bolt head in the center of the belt tensioner and put it on the ratchet.
Put the ratchet and socket onto the tensioner bolt head and turn the tensioner clockwise to relieve the tension on the belt.
Slide the belt off at the idler pulley, which is the top center pulley above the water pump. Finish removing the belt from the rest of the pulleys.
Put the new belt on the bottom pulley, which is the crankshaft pulley, and follow the routing diagram for routing the belt properly on the other pulleys. Leave the idler pulley for last because the idler pulley is the pulley that you will be sliding the belt under once you get the slack out of the belt.
Put the ratchet back on the tensioner bolt head and turn it clockwise with one hand and with the other hand, slide the belt under the idler pulley. Release the belt tensioner and the belt will tighten up against the idler pulley. Inspect it to make sure that the belt is on all of the pulleys.
Crank the truck and let the engine run for two minutes. Turn the truck off and then inspect the belt to make sure that it is still on the pulleys and to make sure that the belt has seated into the grooves on the pulleys.
