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Thread: Oil consumption after CCV replacement

  1. #1
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    Oil consumption after CCV replacement

    OK, I can't figure this one out, so maybe you guys can help. I changed the CCV system on my 01 525i (M54) last fall to avoid the dreaded freezing over the winter. I installed a new cold weather CCV, replaced all the lines, and cleaned the dipstick vent tube and the distribution piece thoroughly (new o-rings all around). All the intake piping was replaced at the same time. I have vacuum at the oil fill hole.

    Everything is great - starts perfect, idles perfect, runs perfect - except that it is now using oil to the tune of more than a quart every 1000 miles. I've seen light puffs of oil smoke after long coasting downhill runs (i.e., high vacuum) on two occasions, but generally there is none.

    It seems I'm not alone in this. There are some on the E39 board who have experienced exactly the same phenomenon after changing the CCV. Some have tried bypassing it with a direct line from the valve cover to the distribution piece, thus applying much higher vacuum to the crankcase; this is claimed to improve the situation.

    I'm not sure how to proceed here. The direct line option is simple enough to kludge up, but it seems, for want of a better term, inelegant. I also wonder if the problem is not too little vacuum but too much; if this is the case, a restrictor in the line from the valve cover to the CCV could improve matters.

    I've thought this through a hundred times at this point, and I think I'm going around in circles. I need new eyes on the problem. Your input is greatly appreciated.





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  2. #2
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    Giving this one a bump in hopes that the pros might have simply overlooked it.





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  3. #3
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    Aloha, friend,

    I saw your thread when running out the door one morning to work, and wanted to give it more consideration, because I know you're good, and weren't likely to be overlooking a leak, or something obvious. I did think about it at work, but forgot to post my thoughts, sorry.

    Staring at me from the wall, at work, was my slack-tube manometer, filled with green water.

    And that's what you need. Guessing whether your vacuum's excessive wouldn't be right, even for someone who knows what "correct" vacuum feels like.

    This is a super tool for BMW's, and cost me about $60. Mine is about 5 feet long, I think it measures thirty inches of vacuum. Fill it with water, and the dye that comes with the manometer, and modify a BMW oil filler cap by drilling a hole in it, and glueing in a vacuum nipple. I believe it's made by "Dyson Instruments", or something similar; found them by Googling "slack-tube manometer".

    You could, it seems to me, make one pretty easily for yourself, too. It's basically a ten-foot piece of clear silicone tube, about 5/16 INSIDE diameter, bent in half at the bottom, to make a big "U". Then it's attached to a "dual" tape measure, which starts dead in the middle of EACH leg of the "U", and reads "up" 30", and "down" 30".

    At the top of each leg of the "U", you'll need to neck the tube down to a vacuum port the same size as the one in the oil filler cap. Fill the silicone "U" HALFWAY; which is to say there'e 30" of air above thirty inches of dyed water, on both legs of the U.

    Hook up one vacuum port on one leg of the U to the vacuum port on your oil filler cap, and read the vacuum you're pulling on the tape measure. You should have 3-6 inches of water as your vacuum.

    Don't know what would have caused you to have more than sufficient vacuum - except maybe, just maybe, a faulty brand new valve.

    Would like to say that I looked at a customer's damned-near perfect '01 525 today, 100k miles and well maintained, garaged, gorgeous. The last great 5 series, Sure, I'd like the 4.4, until I had to fix all the damned leaks, anyway.....

    All the best, my friend.

    Chris

    Chris Powell
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  4. #4
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    Chris, thanks. Not to sound dumber than usual, but is there a reason why a standard vacuum gauge, appropriately attached, wouldn't work here? I have no problem rigging a slack-tube manometer - I've got some tubing lying around here, could probably have one done in an hour - but I've also got a perfectly good vacuum dial gauge hanging on the bench. We are just talking about standard vacuum measurements, aren't we?

    What I can't figure out is exactly why this system is so prone to oil consumption when all the components are new. I seem to recall reading that the M54 is designed to pull additional crankcase gases at light throttle to generate a lean-burn condition for fuel efficiency purposes. Makes me wonder if this "feature" doesn't have a few undocumented bugs.

    Again, thanks for your thoughts. I'll keep you posted.

    -Andrej





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  5. #5
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    The correct crankcase vaccum is 3-6" of water, which isn't much. If you have a gauge that sensitive, then by all means use it. But the odds are that you'll need a manometer for measurements in that range.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    Thought about that, Jim. I'll have a look at the gauge in the morning. Come to think of it, I also have my SK carb sync tool; that measures flow though (Kg/hr, as I recall), but very precisely. I wonder if there's a conversion factor or spec for that....





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  7. #7
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    There is a conversion for inches of mercury to inches of water. Normal vacuum guages read in inches of mercury. One inch of mercury equals 13.6 inches of water. Which means you'll be trying to read less than 1/2" Hg, really damned tough with a vacuum guage.

    Chris Powell
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  8. #8
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    Yeah, that's going to be a problem. Time to dig out that tubing...





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  9. #9
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    Not sorry at all, that I bought my slack tube manometer: Jim (Levie) made me do it, for which I'm eternally grateful.

    Hell, after nearly 900 bucks on the smoke machine, the sixty-something bucks was great. But looking at it, yeah, you can make one; the smoke machine, not so much.

    Chris Powell
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  10. #10
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    Quick update. Got the slack-tube manometer built; it only reads 20" per side, but that's more than enough for this purpose. A quick check with the engine starting from dead cold shows 8" at high idle, dropping to 6" as the idle drops. I'll check the engine hot tomorrow, but initial results suggest vacuum is within spec.





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  11. #11
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    6" is on the high end, but still within spec. So the valve is apparently working, but there could be "intake" leaks on the engine side of the CCV that is causing more flow through the valve, and thus more oil going into the intake than there should be.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    Quote Originally Posted by thejlevie View Post
    6" is on the high end, but still within spec. So the valve is apparently working, but there could be "intake" leaks on the engine side of the CCV that is causing more flow through the valve, and thus more oil going into the intake than there should be.
    So, the suspects there would be the hose connections from the valve cover and the dipstick tube (assuming you mean the crankcase ventilation side, not the intake manifold side). I'll check them again, but as I recall everything was solid. All the hoses are new, as are the O-rings.

    It occurs to me now that I also switched oils at the last change: to Castrol 5w40 from Pennzoil Platinum 5w30 (both full synthetics). I wonder if the former is simply more volatile and is burning off faster, though the rate off loss would suggest something else is at fault, or at least contributing.

    Thanks for your thoughts.





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  13. #13
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    Hmmm.....

    Honestly, I'm not following how leaks are causing more flow; I'd never argue with Jim on something like this; he's most likely right, and I'm missing the concept.

    But while you're smoking for leaks, I'll suggest another couple left-field answers:

    a) Baffles in the valvecover are sludged or clogged: I'd feel better about suggesting this to someone besides you, because I don't see you as neglecting maintenance. But I suppose they could suck more liquid if the air passages became narrowed.
    b) Ruined oil control ring on some piston. I have encountered an M54 that had had the engine replaced after first, oil consumption had increased significantly, then, the car had very little power. Compression was nil on cylinder 6, 30 on #5. Postmortem revealed trashed rings, oil control rings practically melted into the groove. The tech (not me) replaced engine with used, waved bye-bye, but car was still slow. 10k later, car was back, same exact symptoms/ New job was mine. Replaced motor, but then refused to let car leave; tested everything, twice, sent injectors to RCEngineering, etc. Then ran exhaust backpressure test, got 5 psi on rear bank. Used borescope to crawl down header from O2 port, found 3/4 blockage of cat-a-comb, if you'll forgive the poor joke. Replaced both cats with Summit racing units and some fancy welding, and suddenly car was fast, too.

    That was 22,000 miles ago, car runs great. Which came first, the chicken or the egg? The clogged cat, or the trashed oil ring? Dunno. But since you made a slack-tube manometer, I bet you can hook up a normal vacuum/pressure tester to your O2 sensor ports.....

    By the way, you have my great respect, for making your own manometer; many pats on the back, for that!

    Maybe even c) a faulty, brand-new ccv valve, or pinched oil return hose? I would not expect the oil change to be of issue.

    Chris Powell
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  14. #14
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    Quote Originally Posted by bmwdirtracer
    Honestly, I'm not following how leaks are causing more flow; I'd never argue with Jim on something like this; he's most likely right, and I'm missing the concept.
    Normally the crank case is sealed and the CCV only pulls blowby gases from the crank case into the intake. However if air is leaking into the crank case, say from a leaking oil filler cap, dispstick o-rigs, or a bad gasket, more air has to flow through the valve and into the intake to maintain correct vacuum. That additional flow carries more oil into the intake and thus increases oil consumption.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

  15. #15
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    Well, let's hope it's not the melted rings/blocked cat situation. That would make me extremely unhappy.

    I certainly don't skimp on maintenance, but it may be worth pulling the VC and flushing and blowing out the baffles. The oil return line and the dipstick tube are absolutely clear and free; I just had that apart. As for air leaks into the crankcase, the dipstick o-rings and VCG are all new. Oil fill cap hasn't been replaced; I'll do that just in case, but the seal looks good.

    I'll see about rigging up an adapter to put a pressure gauge on the exhaust manifold and see if anything turns up. Maybe I'll throw a couple pics of my manometer design for those who might want to build their own as well.

    It's worth noting that there's no discernible performance problem. The car starts, idles, and runs perfectly.

    Thanks for hanging in there with this one, guys.





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  16. #16
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    OK, more observations. With the engine fully warm it's pulling 5" of water, nicely in spec. Now, just in the interest of experimentation, with the manometer hooked up I yanked the dipstick out to induce a vacuum leak into the crankcase. This dropped the vacuum reading to just over 3".

    This got me thinking about the fact that we're talking about two factors here: vacuum and flow. Measuring vacuum is an indication of the soundness of the CCV system and the function of the valve, but flow through the system is the issue that would appear to contribute to the question of oil consumption. This makes me think back to one of my original ideas: adding a restrictor to the line from the crankcase to the CCV. This should not affect vacuum at all, but would reduce the flow of crankcase gases to the valve.

    Thoughts?

    EDIT: It seems that flow and vacuum are obviously related, but I don't know what that relationship is. This has me searching the internet for engineering tables and charts representing values the significance of which I am not fully aware. Sometimes it's annoying not having an engineering degree.

    Net result so far, though, is that I've got oil consumption that a) began with the CCV replacement (well, got significantly worse with it; it always used a little oil between changes) and b) I can't find the source of. With the CCV in spec, I'm grasping at straws here as to where to go next. I know BMW updated the dipstick design to prevent clogging, but mine is clear. I can't see how the new design (without the separate outer passage for oil draining back from the CCV) would have any other effect on function of the system.

    This is quite frustrating....
    Last edited by 02Pilot; 04-06-2011 at 04:49 PM.





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  17. #17
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    Good thread. Following it until it's concluded.

    Nice work, keep it going.
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    Well, next steps are:

    1) Change the oil. I really don't think the oil (Castrol 5w40) is the culprit, but I'm going to eliminate it as a variable. I'm going back to Rotella 5w40, with which I had much lower consumption.

    2) Pull the valve cover and flush out the baffles. I popped the line off and did a quick visual inspection, which turned up a small amount of gritty sludge, but not enough to cause any significant blockage. This does not mean that there isn't significant accumulation in the baffles themselves, however. I'm a fanatic about maintenance, but I bought the car with 100k on it. Everything under the valve cover was very clean, but sludge accumulates in strange places.

    3) If none of this works, I'm going to yank the dipstick tube and chop the bottom section off, remove the inner section, and weld it back up, in effect replicating the new design.

    If none of that works, I'll probably move to more radical possibilities.





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  19. #19
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    OK, old thread, I know, but this condition still exists and I'm still working through the situation (time has not been all that readily available to tear into it of late).

    I went over everything again with a fine-toothed comb. Reverified the crankcase vacuum at ~5" H2O (hot) with the manometer; pulled the valve cover and manually cleared the baffles - there was some sludge in the corners but nothing was blocked (VCG is new, BTW); replaced oil fill cap; changed oil back to Rotella T6 5w40 (which resulted in a slight improvement in consumption); pulled dipstick tube again and found a slightly pinched O-ring - this was rectified, but it did not appear to have been sufficiently out of shape to be leaking any significant amount of air; rechecked all CCV connections and hoses - all good; inspected air distribution piece and found evidence of more oil than I would like, which suggests that the CCV is indeed the source of at least some of my oil consumption.

    Observation while driving shows that oil only burns enough to be noticed (a small puff from the tailpipe) after a long downhill run with the throttle closed. This suggests that too many crankcase vapors are being pulled in into the intake under high vacuum. As Jim indicates above, this may be due to an air leak into the crankcase, but beyond the oil fill cap, and the dipstick and tube, I don't know of anywhere else it might be allowing air in and not simultaneously leaking oil (and nothing's leaking oil). Maybe there's a place I don't know about.

    On the assumptions that too many crankcase vapors are being introduced to the intake, I decided to try to the idea of restricting the flow of these vapors. This afternoon I fabricated a small restrictor: a short steel tube that fits into the inner orifice of the valve cover vent with a washer welded to the outer end that fits into the inner end of the hose leading to the CCV valve. Eyeballing it, the hole in the washer has probably about a third of the area of the inner orifice of the VC. The fit is snug, and I designed it in such a way as to ensure that no piece could end up somewhere it shouldn't, to fit without any modification, and to be completely and easily removable. Manometer shows that idle vacuum in the crankcase is unaltered, and the car drives normally. I'm going to closely monitor oil consumption to see if things change in any significant way. I have a fairly regular driving pattern for the next few months, so I should be able to get some good data.

    Part of me hates to resort to this sort of thing, but having difficulty clearly identifying a source of the problem has pushed me to it. And I admit, I do like a challenge that involves fabricating stuff.





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    Wow, great thread, my friend, sorry I missed a bit. And thanks for the explanation, Jim, missed it before...

    But now that you just said puff of oil smoke after long decel, I'm hearing the ringing of a distant bell,,,, I seem to recall this being a prominent symptom of a more basic mechanical failure. Valve guides/seals? Damn, can't remember. Just refreshing for my ASE's next month, 13 in all, maybe I'll be reminded? Maybe someone else hasn't had 3 beers, and they remember?

    Chris Powell
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    A puff of oil smoke from the exhaust on application of throttle following an extended closed throttle deceleration is most commonly the result of bad valve seals.
    The car makes it possible, but the driver makes it happen.
    Jim Levie, Huntsville, AL

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    Oh, yeah, I know all about bad valve seals - I own a 2002, after all. And I'm not discounting that they may be contributing. But the amount of fresh oil found in the distribution piece - enough to send a few drops out when tipped sideways after removal - and the fact that oil consumption went up markedly immediately after changing the CCV makes me think that the CCV is playing a part here as well. In effect the mechanical circumstances are the same: high vacuum pulls oil (or oil-laden vapor) into the cylinders. Both the CCV and the valve seals could allow such a condition. This is simply an experiment to see if I can determine what part the CCV is playing.

    What I can't figure out is why BMW is going to all this trouble. It would be infinitely easier to simply introduce vacuum to the crankcase from an intake source before the throttle plate, where vacuum is lower and much more varied, than with all this convoluted plumbing. All my older BMWs did it this way, as did many other cars. I have to assume it's some sort of emissions thing, and I don't like it.





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  23. #23
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    Quote Originally Posted by bmwdirtracer View Post
    Wow, great thread, my friend, sorry I missed a bit. And thanks for the explanation, Jim, missed it before...

    But now that you just said puff of oil smoke after long decel, I'm hearing the ringing of a distant bell,,,, I seem to recall this being a prominent symptom of a more basic mechanical failure. Valve guides/seals? Damn, can't remember. Just refreshing for my ASE's next month, 13 in all, maybe I'll be reminded? Maybe someone else hasn't had 3 beers, and they remember?
    You are correct Chris, I would look long and hard at those valve guide seals, esp since you are over the 100k marks.

    O2pilot, you never did say how many miles you currently have, and what I am thinking is with the new CCV, it may have placed extra stress onto the valve guide seals.
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    Mileage is 137k. I'm not sure how the CCV could place additional stress on the seals, however. If anything, a fully functional CCV should relieve pressure on the seals, no?

    Unless there is some direct causal link between CCV replacement and valve seal failure (which I cannot fathom, but it wouldn't be the first time), the new CCV has some direct part in increasing oil consumption. There are too many cases reported of this phenomenon for it to be coincidental.





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  25. #25
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    Well, let's say maybe the old ccv was causing inadequate vacuum. Then replacing it would increase vacuum, pulling more oil through the seals/guides?

    Chris Powell
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