When replacing the belt tensioner as part of your timing belt service it's recommended that you bleed the tensioner to ensure any air that got into the piston mechanism during transit and storage has been removed.
This is a really simple and straightforward job and a good bit of insurance against tensioner failure. Although I'm using a shop press to do this it equally as easy using a C clamp or a bench vice. Just keep in mind that it's crucial that the piston remain oriented in an upright position otherwise you'll need to repeat the bleeding process.