Originally Posted by McDonaldD

If your v8 x5 is smoking, after prolonged idle: pull off your air intake and push open your throttle flap. It's wet with oil, no? That's what's causing your smoke.

Valve stem seals cannot EVER leak oil into your intake manifold. If Valve stem seals fail, they can only cause a puff of blue smoke on startup. Why? because oil SLOWLY drips down past the seal and into the combustion chamber. Starting the engine instantly burns off the tiny amount of oil and the heat causes the valve stem seal to swell and re-seal...that's it. Valve stem seals do not and cannot cause smoke after prolonged idling.

Please stop espousing the valve stem seal myth. The only reason the "repair" fixes the smoke issue is because your mechanic has to replace every other sealing surface on the top of your motor. The new gaskets renew your engine's vacuum seal. The EGR system needs a constant vacuum in order pull the PRVs closed. No vacuum? PRVs stay open and oil gets pulled into the intake manifold; causing the clouds of smoke that so many have wrongly attributed to valve stem seals. Properly functioning PRVs prevent oil from being sucked into your intake manifold. No oil in your intake manifold, no possibility of clouds of blue smoke after prolonged idle. It has nothing to do with the valve stem seals, themselves. Doing the same job, Sans valve stem seal replacement, will yield the same result. But, you don't have to do the entire job.

There are numerous other things that can be done that are infinitely easier. start identifying your oil leaks: vacuum pump? Oil pressure sensors? Oil filler cap? Dip stick o-rings? Adhering to BMW's oil recommendation of 0-40w? VANOS o-rings? Fix those issues and then, if necessary, move on to replacing the harder parts: intake manifold gaskets; valve and timing cover gaskets

Just please stop telling people to replace their valve stem seals.