The engine fan can be very tough to get off without the correct tool. You would pull the clips on the shroud and pull it upwards, then set it back on the fan blades. There is one central bolt which attaches the fan to the fan hub, it's an 8mm allen head, there is a tool MB sells that makes it easier to get on and off. On the fan hub, there are 2 holes drilled in to the back side, either one of which can be used to hold the hub from turning. On the aluminum housing of the fan bearing bracket, there are 2 notches cast in, more on the drivers side of the bracket. MB sells a tool, like a long steel rod with a bend on the end, the bent part is placed between the 2 notches, then while turning the central fan bolt (counterclockwise), the tip of the rod end is rubbed against the back of the fan hub, you want the tip to engage in to the hub and hold it from turning. After removing the bolt, the fan can be wiggled off the hub and the shroud and fan assembly both can be removed. When reinstalling, the central bolt is torqued to 40nm. Lets hope your central bolt isn't overtightened. As you can imagine it gets to be a big mess if the allen head part of the bolt gets rounded out.