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  #21  
Old 05-19-2016, 08:44 PM
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Quote:
Originally Posted by stiubhartach View Post
I would be very surprised if a valve stem seals were leaking enough under vacuum to show visible smoke, but not leaking while the engine is off. Did you try pouring oil into the return passage and watching flow down? That's a hard place to clean.

This I some basics on valve seals:

Automotive Valve Seals: Symptoms Smoke at Startup


This is great post on the CCV system in the n62. Specifically post 18 has some more tests.

http://www.bimmerforums.com/forum/sh...8#post25763768
Trust me, I did make sure there was no obstruction to oil flow. I just read a post where another DIY whose smoking issue at idle was NOT as a result of valve stem seals leak but as a result of vacuum leak! It's a very interesting thread and concurs with you.
http://www.xoutpost.com/bmw-sav-foru...lue-smoke.html

He, like you, does not believe that smoking only at idle is a valve stem seal leak. Looks like the mechanics have been taking us for a ride or what?

I just got some pcs seals for the passenger side as that is leaking and, guess what, only the passenger side exhaust leaks.

I will report tomorrow if that fixes anything.

http://www.xoutpost.com/bmw-sav-forums/x5-e53-forum/90922-solved-engine-failsafe-after-valve-cover-seal-replacement-blue-smoke.html

"A.) Immediately after a cold startup - the first startup after a prolonged period of the engine being off, like sitting in your garage over night?
If so, valve stem seals could be your issue; but I believe this to be a limited failure only seen in the early 745i.

B.) Or, like mine, does the smoke appear as an embarrassing cloud of shame - typically after accelerating from prolonged idling, like sitting at a really long stop light or stop and go traffic...?

Cause of A.)Valve Stem seals only leak down, meaning they have to sit for a long time and be cold (small) enough for oil to slowly drip past them; theoretically, it could deteriorate to the point where would leak all of the time, but you’d see the smoke issue as a constant factor, rather than just when the engine is warm. When valve stem seals get warm, they expand. The expansion would reseal the path the oil was leaking through until the seal cooled to the point where it was small enough for oil to seep past. This is why failing
valve stem seals can cause smoking at startup - oil has dripped past, collected in your cylinder, and then gets burned off the next time the car starts….and the smoking stops when it gets warm…only to return the next time your car has been sitting and is cold.

Cause of B.) is caused, essentially, by a vacuum leak that prevents the PRVs from sealing...drawing oil into your intake.
"
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  #22  
Old 05-19-2016, 09:02 PM
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Quote:
Originally Posted by upallnight View Post
At WOT (wide open throttle) there is very little manifold vacuum. At idle because the throttle plate is close and there is just a tiny gap for air to pass through, the vacuum is High. Don't believe this, connect a vacuum gauge at an manifold inlet such as the brake booster and see the vacuum at idle and the vacuum when the throttle is opened.
Of course, that's right.........I was having a little brain fade there.....
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  #23  
Old 05-19-2016, 11:12 PM
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Your are correct that idle is the highest point of vacuum in the intake manifold in all normal cars. . BMW Vanos is slightly different in that the throttle plate is controlled by the computer and is not used for rpm control and defaults to fully open when the engine is running. That's why there is a supplementary vacuum pump.
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  #24  
Old 05-19-2016, 11:16 PM
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Good links to the vacuum link threads. Never thought of that angle, but it makes sense. Here's a little more basics from your very knowledgeable poster.

http://www.xoutpost.com/bmw-sav-foru...v-details.html

Note: my x5 had the valve cover gaskets replaced at the dealer.
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  #25  
Old 05-20-2016, 01:02 AM
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Here's another one by the same author:
http://www.xoutpost.com/bmw-sav-foru...ml#post1011117

If fixing all vacuum leaks stops my smoking issue at extended idle, then the valve stem seals replacement as the default repair for this issue as recommended by professional mechanics, in my book, is going to be the greatest BMW auto repair scandal equivalent to the VW tdi and now Mitsubishi mpg saga.
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  #26  
Old 05-22-2016, 03:03 PM
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Interesting link. The AGA valve stem tool is what caught my attention. If you were trying to fix a smoking problem and pulled the valve covers to replace the gaskets and clean the vacuum hoses etc, the tool would allow valve stem seal replacement without pulling the heads and cams.

I'm a firm believer in replacing wearable components while you are in the area. This would mean that a valve stem seal replacement would only be another couple of hours rather than an extra 20 hours work. The extra effort would be worth the insurance of new seals.

Tool: 11-12-7-568-838 Valve Stem Seals | AGA Products
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  #27  
Old 05-22-2016, 04:41 PM
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I replaced the seals that are on the valve covers (cps etc) but smoking persists on very extended idle- idled for 20 minutes and there was a huge plume of smoke when I hit the accelerator. There was some improvement in performance so I must have had some vacuum leaks - some sensors had signs of oil leak.

I'm taking her in for a thorough smoke test to rule out any vacuum leaks. If no vacuum leaks are found then I will know I'm dealing with valve stem seals leak, right?
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  #28  
Old 05-22-2016, 05:48 PM
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First try changing the engine oil to something a little thicker, like Mobil 1 10W-40 High Mileage.
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  #29  
Old 05-23-2016, 03:31 PM
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Quote:
Originally Posted by X5only View Post
I replaced the seals that are on the valve covers (cps etc) but smoking persists on very extended idle- idled for 20 minutes and there was a huge plume of smoke when I hit the accelerator. There was some improvement in performance so I must have had some vacuum leaks - some sensors had signs of oil leak.

I'm taking her in for a thorough smoke test to rule out any vacuum leaks. If no vacuum leaks are found then I will know I'm dealing with valve stem seals leak, right?
Possibly. Before you drop a couple thousand in repairs on seals, take a physical look inside the intake manifold. I used a fiber optic scope, but the hole is pretty big. You could even put a phone in side I think. Another owner temporarily replace the CCV line with clear PCV line and diagnosed it that way. If you see no oil and it is still smoking, then it is probably seals ( or rings). Rings won't leak while sitting, but will smoke while running, not just at idle. I think that is rare though. Note the dipstick can be a vacuum leak too. Also you can diagnose vacuum level in the crankcase at the dipstick, but I don't remember the particulars.

Here's another thread.

http://www.xoutpost.com/bmw-sav-foru...cuum-line.html
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Old 05-23-2016, 05:47 PM
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The seals on top of the valve covers are very cheap (spent no more than $40 for sensor seals, oil fill cap, etc). There was no oil on the passenger side PCV line that connects on top of the intake manifold- it was bone dry. The driver side PCV line had some oil and the exhaust tips on that side is the one that was smoking heavily (passenger side tail pipe had very little smoke). I'd changed the seals on the dip stick and installed a new oil filler cap (it was leaking oil and there were signs of oil wetness on the side of the valve cover).

Great idea on using a clear pipe to replace PCV lines. I have some old PCV lines and I can cut off the tips and join them to a clear pipe.

I want to conclusively prove it's the valve stem seals that are leaking before embarking on their replacement.
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