BMW Repair: 318 BMW ti - 70k miles, purge solenoid, 318 bmw

Question
Don,

P0442 - Engine code.  The gas cap was replaced several times.  I've been reading on the internet that it could be a leak in the fuel expansion tank.  Where would this be in the car?  I also read that there could be a faulty purge solenoid or the vent solenoid. Where would these sensors be?  Any advice would be greatly appreciated.  What would you recommend to do?  

Answer
Your reading was correct it could be a leak there,purge solenoid or the vent solenoid.Searching for the answer by part elimination isn't where I go with the codes ones gets.Your best bet if you plan on keeping the car and continue to work on it you need a Bentley manual.It goes in to detail alot more than I could.Calling Bavarian Autosport 1-800-535-2002 they will help with your needs.