How do you replace the idler tension pulley on an Oldsmobile?

It's easy, but you'll need a helper. Once you have a replacement ready to go, find a socket that fits the pulley bolt on your old one. Ensure that there is a belt routing diagram under the hood or take a couple photos or draw one before you take off the belt. Use a long handle socket wrench to pry on the pulley against spring tension using bolt to create slack in the belt. At the same time have your helper slip it off one of the top accessories with a screwdriver. Once belt is off, remove bolt that holds tensioner bracket to block. Reverse to reinstall except this time your helper will be trying to put belt over last accessory while you hold pulley. Bump the engine a few times before you start it to ensure ribs on belt backside have all fallen into their grooves.