The next time you utilize a drive belt, timing belt, or timing chain, you’ll likely have to loosen a tensioner pulley to eliminate 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 various other timing belt tensioners are loosened by simply Car Pulley Belt 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 automobiles with timing chains, though some are used in combination with timing belts. Hydraulic tensioners are driven by oil pressure from the engine 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 info, and you may have 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. Take away the lock only after 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 the teeth and keeps drive belts from slipping and making noise. To loosen a drive belt springtime tensioner pulley, refer 1st to the restoration manual or owners manual’s specific season, 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 pressure on the belt. You will have to hold some spring 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, then cool off the tensioner screw. Push the pulley toward the other pulleys or accessories, loosening the belt.
Spring tensioner pulleys, since the name implies, use 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.