Replacement of a timing belt idler pulley is a similar procedure to that of other timing components, such as the timing belt tensioner. It is a fairly extensive process, one that requires a significant amount of tools and training. The procedure can lead to engine damage if performed improperly.

To replace a timing belt idler pulley, a technician needs to gain access to the front of the engine. This often requires lifting and supporting the vehicle in the air. Shields, guards, covers, ducts, drive belt, and even the radiator might need to be removed as well.

With those items out of the way, a typical timing belt idler pulley replacement involves the following general steps (the procedure differs from one vehicle make and model to the next):

• Remove the water pump (on some models)
• Detach the drive pulley on the crankshaft
• Remove any engine accessories (AC compressor, alternator, power steering pump, etc.) that are in the way of the timing cover
• Remove the valve cover(s) (on some models)
• Unbolt and remove the timing cover from the front of the engine
• Synchronize the timing marks on the camshaft and crankshaft pulleys and align to top dead center
• Remove the timing belt idler pulley (s)
• Dislodge the crankshaft pulley and timing belt
• Install a new belt - usually done in tandem with the idler pulley - taking care to align to the timing marks
• Reinstall all components and add fluids as necessary
• This abbreviated list of steps does not account for differences between engines, whether your has single or dual camshafts and other variables. It is common to replace not only the idler pulley(s), but also the timing belt and even the other pulleys on which the belt rides. If your engine has a water pump that is driven by the timing belt, that too will be recommended for replacement. The procedure is similar if your engine has a timing chain rather than a belt. If the procedure is not done properly, your engine could fail to run, run poorly, or suffer severe internal damage.