Take the 4 bolts completely out of the housing. Remove the 2 bolts holding the Vanos lubrication connection piece (actually easier if you remove one of the vanos lub flex tubes to get this piece completely out of the way).
Now comes the tricky part. You must pull the housing forward and up with a side-to-side rocking motion. As the O-rings on the three "tubes" at the back of the housing start to come loose, you will have a problem with the thermostat catching on the top of the water pump. Keep moving side-to-side and up an it will clear.
Better buy the Orings and perhaps some spairs for reassembly. It is real easy to cut them. Lubricate them before you start with a silicon spray and insert gently with the same side-to-side motion. Keep looking on the engine under the tubes for a piece of Oring rubber to show up. If you see, you cut one and must redo.