The first sign of wear is “noise”. A tensioner that sounds bad usually is bad. While the engine is running, listen to hear if any noise is coming from the timing cover or front assembly. Bad bearings make a high pitched “whine” or “growling” noise after the engine has been started. If there is noise, and it is identified as coming from behind the timing cover, you should:
>Remove appropriate components in order to remove the timing belt and check the idler pulley for failure. The idler pulley accounts for about half of all tensioner failures.
>Misalignment of the timing belt can cause premature failure of the idler pulley or the pulley on the tensioner, as well as the belt. Generally, this indicates that the tensioner or idler is not attached to the mounting location on the engine correctly or the bearings for the tensioner, idler or both, have worn and have excess “play”. It is important that the belt and bearing alignment is correct. Do not reuse the timing belt, tensioner or idler if misalignment is found, replace them with new components to avoid engine damage or failure.
>With the timing belt removed, check for side to side play or “rocking” on both the idler pulley and tensioner pulley. Replace if any movement is detected.
>With the timing belt removed, check both the idler and tensioner pulleys for roughness when rotating the bearing. The idler & tensioner should spin freely and smoothly. Replace bearing(s) if roughness is determined.
Inat recommends replacing timing belts, tensioner and idlers at 60,000 to 80,000 miles to prevent unnecessary damage to your engine. Don’t forget to check for oil leaks while investigating bearing noise. In order to avoid premature seal failure, always make sure the sealing surface is smooth before replacing camshaft or front crankshaft seals that show signs of leaking.