If you've got a 4.0 litre engine than you've got a Automatic belt tensioner on the engine. Sits to the right of the alternator. If your belt is loose, than you need to check that the belt is on properly on all the pulleys, or if you have the right belt. If the belt was made for a motor with A/C and yours doesn't have that, then the belt will be to long. Check with your local auto part supply store. Hope this helps...... For info on how to route the belt, get a chiltons manuel and it will have a diagram.