Next time you utilize a drive belt, timing belt, or timing chain, you’ll likely have to loosen a tensioner pulley to remove it. Following these general suggestions and specific instructions from your owners manual or restoration manual, your belt or chain will function for the life of your car.

Toyota and other timing belt tensioners are loosened by simply 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 almost always situated in the timing case, mostly on automobiles with timing chains, while some are used in combination with timing belts. Hydraulic tensioners are driven by essential oil pressure from the engine oil pump and could press on a tensioner pulley (timing belts) or pressure slipper (timing chain). You will likely need the entire year, make, and model details, 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 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 the teeth and helps to keep drive belts from slipping and making sound. To loosen a drive belt springtime tensioner pulley, refer initial to the restoration manual or owners manual’s specific calendar year, 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 pressure on the belt. You will have to hold some springtime tensioners while slipping on a fresh belt. Others may have 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, then cool off the tensioner screw. Press the pulley toward the additional pulleys or accessories, loosening the belt.
Spring tensioner pulleys, as the name implies, use a spring to hold tension on the belt. Most, if not all, springtime tensioner pulleys are NAI tensioners and include a hydraulic damper. They are more technical and costly but don’t require changes and are less prone to user error.