Originally Posted by McDonaldD (Post 1011117)

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.

Originally Posted by McDonaldD (Post 1011117)

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.

Originally Posted by BMW_TUNER (Post 1011671)

I have taken apart the intake and seen a heavy film of oil in the intake but no puddles. Is a film a sign that there are other sealing issues or will it be a puddle? My 4.8is gets pretty smokey after extended idle but produces no smoke what so ever at startup no matter the oil weight or temperature.

Originally Posted by Doru (Post 1011681)

In my case, the throttle body was quite clean. I had no smoking issue at start-up, but it was heavy after the engine warmed up to operating temp, and had to idle at stop signs. Oil consumption was heavy at a rate of about 1qt/400 Km, whatever that is in miles, you would think it was an old 2 stroke engine.......

back to normal now.

Originally Posted by BMW_TUNER (Post 1011682)

In you case was it Valve guide seals or another issue?

Originally Posted by A B Able Truck (Post 1011136)

Historically, I'm with you all the way. But since AGA has invented their valve stem seal tool, I've had to adjust my repair recommendations in this matter due to the labor cost savings. Yes if there is oil in the intake - that needs to be remedied first. And yes, the crankcase needs to be sealed for the PRVs (CCVs) to worked as designed. But the things to consider are;
- If you're going to replaced your valve cover gaskets, you may as well replace your valve stem seals if this tool is available.
- In theory, the valve stem seals are as the valve cover seals in respect to a sealed crankcase system for proper ventilation function.

Originally Posted by A B Able Truck (Post 1011136)

- In theory, the valve stem seals are as the valve cover seals in respect to a sealed crankcase system for proper ventilation function.

Originally Posted by BMW_TUNER (Post 1011671)

I have taken apart the intake and seen a heavy film of oil in the intake but no puddles. Is a film a sign that there are other sealing issues or will it be a puddle? My 4.8is gets pretty smokey after extended idle but produces no smoke what so ever at startup no matter the oil weight or temperature.

Originally Posted by Doru (Post 1011680)

It's weird, because I had no oil in the throttle body, yet I had HEAVY smoking after more than 2 minutes idling. I also had an unusually high oil consumption.
As A B Able truck said, once you work on those seals, you "normally" would replace every seal....
But there are people who tried mitigating the smoking issue by only changing the VCG and related gaskets/seals, and the end was only a reduced tailpipe smoking result.....So I guess, there are situations & situations, and not a myth.

Originally Posted by McDonaldD (Post 1011713)

Sure, if you're in there, why not? But what I don't get: The smoke comes out of the exhaust pipes, no? Why not replace your headers, cats, oxygen sensors, mufflers and exhaust pipes? Oh, don't forget the chrome tips; there's a tool for that, too, no? I'm sorry for being a jerk but one may purchase any number of tools to replace any number of parts. People are attempting to repair their cars. They're not dabling in buying tools or replacing parts for replacement's sake. If you're replacing for replacement's sake, why not Start afresh? Buy the new F15 and move on?

I, too, fell prey to the "while you're at it" crowd. I replaced the coolant transfer pipe while replacing my upper engine seals. There was a useless tool for that as well...but thats another tale about why one should understand a part's potential for failure BEFORE assuming failure could, in any way, exhibit symptoms stated as the reason for said part's replacement. On the e53's N62? no. On previous versions, possibly? Anyway.

My comments about the valve stem seal fallacy narrowly apply to an engine that meets ALL of the following criteria:
- at operating temperature
- after a period of prolonged idle
- puffs/clouds of bluish smoke envelope the world behind you as you accelerate from the aforementioned state of prolonged idle.

My comments do not broadly apply to any of following:
- Pure white whisps, puffs, clouds of smoke - Congrats to the >99% that have found the dew point. My condolences to the unlucky <1% that have coolant making its way into their combustion chamber (and, likely, oil)
- bluish puff or cloud on startup - you have found the fabled valve stem seal issue. The automotive world and modern science would like to know, please, how you managed to torture your vehicle into such a sad state of disrepair. Please join the <1% in the coolant club as you have likely severly overheated your engine.

If your vehicle falls into the narrowly defined yet widespread blue-cloud-off-of-idle problem, continue reading.



The valve stem seals do not contribute to the failure of the crank case ventilation system in the way you think they do. The seals expand with heat, not contract. This means, while hot, the seals are larger than they are while cold. After the engine cools, the valve stem seals shrink, allowing oil/air to slip past. If the valve stem seal were to fail, it would fail first while cold. Sure, a puff of blue smoke on startup may go unnoticed. Say you never notice the puffs of smoke on startup and the valve stem seal failure progresses to a point where they fail to seal even while warm/hot; they're just always leaking. This, you have asserted, is the point of failure that would cause crankcase ventilation failure. BUT it does not make the previous symptoms go away. It would smoke from oil leaking down into the cylinders AND from such a state of catastrophic failure that this new blowby path overcomes the vacuum in the crankcase. It would smoke on cold startup and hot startup. It would just smoke. ALWAYS. Yet this is not the case. The issue I, and countless others, have experienced only smokes at a very particular time: a cloud of bluish smoke after prolonged idle at operating temperatures.

My point is, valve stem seals cannot fail in the way you, A B Able, have stated without also exhibting the other symptoms. No oil-cloud on startup, no failed valve stem seal.



You should never have oil, film or otherwise, in your intake manifold. The intake manifold should be pristinely dry and free of ANY residue. Oil in your intake can only come from the PRVs/crankcase ventilation system failure. This is the failure that causes oil consumption.



If you meant your intake manifold was clean, disregard the rest of this: Your throttle body will likely always be clean. The intake manifold, behind it, will be coated with oil. You'd have to push on the top of the throttle plate and then peer in with a flashlight. My intake manifold's plastic was supposed to be green but instead it looked black. You likely will not see pools of oil as the intake is quite deep. The reason the throttle body is clean while the intake manifold is smothered in oil is because the crankcase ventilation system bypasses the throttle body. The vents connect directly to the intake manifold: Above and below the throttle body.