It is a 2007 E class 320 cdi estate. The longest pipe is heavily corroded at the rear O/S and needs replaced. I have taken off the covers and see that it is only the last two feet of pipe that has any corrosion. The rest is as new but appears to be one piece from the flexi-hose at the rear right to the brake pump in the engine bay. Trouble is the heat shield at the front makes it look a nightmare to fit replacement pipework so will cut out the corroded section and attempt to flare the sound steel pipework and join in a short length of replacement Kunifer to the flexi-hose. Should I encounter any difficulty in bleeding out the system given that I will need to empty that long length of pipework? Do I do the bleed with the engine off, or on, to activate the pump? Will it involve having to use Star because of the pump or can I do this job as normal (engine off) and use my wife on the pedal and me on the bleed screw as normal?