Hi, I'm new to this forum. My 535i's water pump failed which resulted in blown radiator hoses, blown headgasket and, we think, a piston has ben dragged. (nasty deep knocking sound at front of engine when it runs) . We have obtained a second hand engine and are planning to do the swap ourselves. We are old car enthusiasts and have lots of mechanical experience but have not worked on anything this modern before. I am wondering if anyone who has done this already could share any tips, known problems to look out for etc before we start. We have the Haynes manual. Thanks.