The accessory drive belt on the 2003 Ford Focus is a single serpentine belt that runs all the accessories. The spring-loaded tensioner maintains the tension on the belt. At each oil change -- or at least every three months or 30,000 miles, check the belt for glazing or cracking. The glazing smoothes the fabric of the belt and is caused by slippage. The belt could slip because it stretched past the scope of the tensioner from normal wear and tear, or the one of the pulleys could be locking up.
Check to ensure that the belt routing diagram is legible. It is usually located near the radiator beam or on the underside of the hood. If not, sketch a diagram of the belt routing diagram before starting.
Jack up the front of the vehicle, using the floor jack. Support it with jack stands. Remove the splash shield from under the front of the vehicle to gain access to the tensioner.
Fit the appropriate socket on the bolt in the center of the tensioner pulley. Rotate the pulley toward the center of the engine to relive tension on the belt. Lift the belt off the pulleys.
Route the new belt around the pulleys, starting with the crankshaft pulley and leaving the tensioner pulley until last. Rotate the tensioner pulley toward the engine and slide the belt over the tensioner. Allow the tensioner to rotate back into place. Reinstall the splash shield. Lower the vehicle off the jack stands, using the floor jack.
