Next time you utilize a drive belt, 
Car Pulley Belt timing belt, or timing chain, you’ll likely have to loosen a tensioner pulley to eliminate it. Subsequent these general guidelines and specific instructions from your own owners manual or restoration manual, your belt or chain will function for the life span of your car.
Toyota and various other 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.
Hydraulic (not hydraulic-damped) tensioners are nearly always positioned in the timing case, mostly upon automobiles with timing chains, though some are used with timing belts. Hydraulic tensioners are run by oil pressure from the engine oil pump and may press on a tensioner pulley (timing belts) or pressure slipper (timing chain). You will likely need the year, make, and model details, and you may need to use special equipment 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 installed 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 tooth and keeps drive belts from slipping and making noise. To loosen a drive belt springtime tensioner pulley, refer initial to the repair manual or owners manual’s specific calendar year, make, and model details.
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 tension on the belt. You’ll need to hold some spring tensioners while slipping on a new belt. Others may have a locking mechanism, such as 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. Push the pulley toward the additional pulleys or add-ons, loosening the belt.
Spring tensioner pulleys, because 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 complex and costly but don’t require adjustments and are less susceptible to user error.