It is necessary to put on the necessary gears and other precautions and warnings before commencing with the job. If you have to replace any line or hose, lose as less of fluid as possible, to do so first remove the master cylinder reservoir cap and place a piece of cellophane over the opening. The flexible hoses can be fitted with a brake hose clamp and the metal brake line fittings can be plugged or capped if necessary the moment they are disconnected; but one must be careful not to allow dirt to get into the system. Any fitting should have a rag placed underneath it to allow it capture any dripping fluid. Before removing the flexible hose you must first loosen the brake line filling nut before releasing the spring clip on the hose. In order to release brake line fittings, one has to use a flare-nut wrench while the area should be clean when disconnecting. If it is to replace a brake line it can be bought pre cut with the fitting nuts and end flares from the BMW dealers or can be made from kits from motor accessory shops though it required the measurement of the original to be very accurate. During installation do not over tighten line fittings, make certain that all the lines and hoses are properly routed without kinks and fasten in clips or brackets where provided. After installation pull the cellophane over the reservoir, purge the hydraulic system, wipe clean any over sprayed fluid and inspect for leaks.