Lauren: PCV= Positive Crankcase Ventilation; but in a real sense, it IS a pressure control valve of sorts. If clogged, pressures build up that can 'pop' your rear main seal (usually the first to go), your front main seal, etc. The 740's that I have looked, over my indulgent mechanic's shoulder, are on the driver's side of the engine, behind the water pump, below the injectors: not too easy to get at. Newer engines may have them more conveniently placed, I dunno. Go to the '700-900 FAQ' and check out as many sections as possible, even if you think that they overlap, are redundant, repeat themselves...oh my. look what I've done: a self-fulfilling prophecy! Anyway, READ first, then get back here to the BrickBoard, and hope that the Bentley's gets there soon. Good Luck, amiga.---PD.