Next time you work with a drive belt, Car Pulley Belt timing belt, or timing chain, you’ll likely have to loosen a tensioner pulley to remove it. Following these general guidelines and specific instructions from your owners manual or restoration manual, your belt or chain will function for the life span of your car.

Toyota and other timing belt tensioners are loosened by simply removing them from the engine. You must slowly compress them in a bench vice and lock them with a pull-pin before reinstallation.
Hydraulic (not hydraulic-damped) tensioners are almost always situated in the timing case, mostly upon vehicles with timing chains, though some are used in combination with timing belts. Hydraulic tensioners are powered by essential oil pressure from the engine essential oil pump and may press on a tensioner pulley (timing belts) or stress slipper (timing chain). You’ll likely need the entire year, make, and model information, and you may have to use special tools for this kind of tensioner pulley.
Typically, a hydraulic tensioner needs to be “reset” and locked after removing it from the engine. Remove the lock only after the tensioner, pulley, or slipper, and timing belt or timing chain are set up and aligned.

The spring maintains tension, as the hydraulic damper keeps it from bouncing under load changes. This prevents timing belts and timing chains slapping and jumping teeth and continues drive belts from slipping and producing noise. To loosen a drive belt springtime tensioner pulley, refer first to the restoration manual or owners manual’s specific year, make, and model info.
You may need a special tool, but many spring tensioners have a square hole, for a 3/8” or 1/2” breaker bar, or a hex or square protrusion for a wrench or socket. Using the appropriate tool, release tension on the belt. You’ll need to hold some spring tensioners while slipping on a fresh belt. Others may have a locking mechanism, like a hole for a locking pin or hex crucial.

To loosen an NAI tensioner, loosen the locking nut or bolt, then back off the tensioner screw. Drive the pulley toward the various other pulleys or accessories, loosening the belt.
Spring tensioner pulleys, since the name implies, make use of a springtime to hold tension upon the belt. Most, if not all, spring tensioner pulleys are NAI tensioners you need to include a hydraulic damper. They are more technical and costly but don’t require adjustments and are less prone to user error.