Next time you work with 
a drive belt, timing belt, or timing chain, you’ll likely need to loosen a tensioner pulley to eliminate it. Following these general guidelines and specific instructions from your 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 by simply 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 located in the timing case, mostly on automobiles with timing chains, though some are used with timing belts. Hydraulic tensioners are driven by oil pressure from the engine essential oil pump and could press on a tensioner pulley (timing belts) or stress slipper (timing chain). Car Pulley Belt You’ll likely need the entire year, make, and model info, and you may need to use special tools for this type 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 the teeth and keeps drive belts from slipping and producing sound. To loosen a drive belt springtime tensioner pulley, refer 1st to the restoration manual or owners manual’s specific yr, make, and model details.
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 tension on the belt. You’ll need 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 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, since the name implies, make use of 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.
