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

Toyota and various other timing belt tensioners are loosened by simply removing them from the engine. You need to gradually compress them in a bench vice and lock them with a pull-pin Car Pulley Belt before reinstallation.
Hydraulic (not hydraulic-damped) tensioners are almost always positioned in the timing case, mostly on vehicles with timing chains, though some are used with timing belts. Hydraulic tensioners are driven 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 will likely need the year, make, and model information, and you may have to use special equipment for this type of tensioner pulley.
Typically, a hydraulic tensioner must be “reset” and locked after removing it from the engine. Take away the lock only after the tensioner, pulley, or slipper, and timing belt or timing chain are set up and aligned.

The spring maintains tension, while the hydraulic damper keeps it from bouncing under load changes. This prevents timing belts and timing chains slapping and jumping the teeth and continues drive belts from slipping and producing noise. To loosen a drive belt springtime tensioner pulley, refer initial to the repair manual or owners manual’s specific year, make, and model information.
You might 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 stress on the belt. You will have to hold some spring tensioners while slipping on a fresh belt. Others may possess a locking mechanism, such as a hole for a locking pin or hex essential.

To loosen an NAI tensioner, loosen the locking nut or bolt, after that cool off the tensioner screw. Drive the pulley toward the various other pulleys or components, loosening the belt.
Spring tensioner pulleys, because the name implies, make use of a spring to hold tension on the belt. Most, if not all, springtime tensioner pulleys are NAI tensioners and include a hydraulic damper. They are more technical and costly but don’t require adjustments and are less susceptible to user error.