The next time you utilize a drive belt, timing belt, or timing chain, you’ll likely need to loosen a tensioner pulley to eliminate it. Subsequent these general guidelines and specific instructions from your own owners manual or repair manual, your belt or chain will function for the life of your car.
Toyota and additional timing belt tensioners are loosened simply by removing them from the engine. You must slowly compress them in a bench vice and lock them with a pull-pin before reinstallation.
Car Pulley Belt hydraulic (not hydraulic-damped) tensioners are nearly always located in the timing case, mostly on vehicles 
with timing chains, while some are used in combination with timing belts. Hydraulic tensioners are powered by essential oil pressure from the engine essential oil pump and could press on a tensioner pulley (timing belts) or tension slipper (timing chain). You’ll likely need the year, make, and model information, and you may have to use special tools 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 following the tensioner, pulley, or slipper, and timing belt or timing chain are installed 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 helps to keep drive belts from slipping and producing sound. To loosen a drive belt spring tensioner pulley, refer first to the repair 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 pressure on the belt. You will have to hold some springtime tensioners while slipping on a new belt. Others may have a locking mechanism, like a hole for a locking pin or hex key.
To loosen an NAI tensioner, loosen the locking nut or bolt, after that cool off the tensioner screw. Force the pulley toward the additional pulleys or add-ons, loosening the belt.
Spring tensioner pulleys, because the name implies, use a springtime to hold tension on the belt. Most, if not absolutely all, spring tensioner pulleys are NAI tensioners and include a hydraulic damper. They are more technical and costly but don’t require modifications and are less prone to user error.