The BMW 4.4 engine has a couple of wide diameter breather pipes that run across the top of the back of the engine. It seems common for these to perish, some people put the perishing down to the material being incompatible with ethanol that is in modern day petrol, others put perishing down to material not being compatible with oil/HC's that inevitably make there way into breather pipes. At the time of design there probably wasn't ethanol in petrol, I tend to agree with the ethanol idea because before ethanol was in petrol we LPG installers could use LPG pipe for petrol but modern petrol causes LPG pipe to similarly perish, similarly the BMW4.4 breather pipes didn't seem to have a problem before ethanol. Since the pipes feed into the back end of the inlet manifold, leaks in them amount to a vacuum leak. I've changed them on a number of L322's that I've converted to LPG - even if there isn't a leak to start with, moving perished pipes around during other work can cause them to break up. By perishing I mean the pipes tend to become gummy, almost like they're melting, become more flexible and easily tearable. There comes a point in the process where in a cross section of pipe it would be difficult to make out where the pipe starts and the gum/oil ends. The pipes are fairly easy for a home mechanic to change and, as I remember, cost a total of around £35 from BMW dealers who seem quite used to supplying these specific pipes (common problem).
Swapping tranny fluid is something I do early on all cars I buy, particularly in autos if it doesn't look or feel like I think it should, I'll also swap coolant, even brake fluid if that looks old. But there is the possibility of causing an old box to whine or affect the shift by swapping in new fluids even of the correct spec. And getting correct spec can involve a bit of research, especially on boxes that were supposedly filled for life.
Simon
