The next time you utilize a drive belt, timing belt, or timing chain, you’ll likely have to loosen a tensioner pulley to remove it. Subsequent these general recommendations 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 need to slowly compress them in a bench vice and lock them with a pull-pin before reinstallation.
Hydraulic (not hydraulic-damped) tensioners are nearly always located in the timing case, mostly on automobiles with timing chains, while some are used in combination with timing belts. Hydraulic tensioners are run by essential oil pressure from the engine oil pump and could press on a tensioner pulley (timing belts) or tension slipper (timing chain). You will likely need the year, make, and model info, 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 following 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 tooth and helps to keep drive belts from slipping and making sound. To loosen a drive belt spring tensioner pulley, refer initial to the repair manual or owners manual’s specific yr, make, and model info.
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 springtime tensioners while slipping on a fresh belt. Others may possess a locking mechanism, such as a hole for a locking pin or hex important.
To loosen an NAI tensioner, loosen the locking nut or bolt, after that cool off the tensioner screw. Force the pulley toward the various other pulleys or components, loosening the belt.
Spring tensioner pulleys, as the name implies, use a springtime to hold tension upon the belt. Most, if not absolutely all, springtime tensioner pulleys are NAI tensioners and include a hydraulic damper. They are more complex and costly but don’t require changes and are less susceptible to user error.