lower deck to lowest setting, remove key from ignition, let tractor cool down, locate upper idler arm and try to move arm up and down by hand, if there is little to no movement it's ok for now, if you find excessive up and down movement the idler assembly mount bolt needs to be replaced. please read my threads for a permanent repair.
http://www.lawnmowerforum.com/simpl...plicity-belts-braking-problem-resolution.html