1992 850i M70 engine oil burn in one bank

[aramis001]

My son has a 12992 850i which is suffering from oil burning on all 6 cylinders on the passenger side. We changed the valve seals and PCV valves on both sides. The spark plugs and the residue inside the cylinders are indication that the burn is on one side of the engine only. The blue smoke from one bay supports this assumption. The following are the symptums, i would appreciate feedback on what the forum members think of the root cause.

- Oil consumption at 1 quart every 300 miles.
- Tried regular as well as synthetic oil, including Mobile 1 and Purple oil. Not much of improvement
- The bad side exhaust (passenger side) will pretty much immediately start white steam when the engine starts running. The driver side (good side) will take few minutes until the engine starts warming up.
- The steam from the bavd side pretty much remains until the engine is relay up to temperature.
- 3-4 minutes of running, i see blue smoke on the bad side. It goes away after few minutes and then comes back.
- The blue smoke will be more dense when revving the engine.
- Wont see any smoke during regular driving. There will be smoke when revving engine from stop position (red lights etc)
- No check engine lights.
- Pretty much all spark plugs on the bad side show heavy residue.
- Drove the car for few weeks with PCV valve completely removed to prevent oil vapors from entering the intake manifold. ( i plugged them so wont lose vacuum). No change in oil consumption levels. (therefore i don't think its oil vapor of PCV issue)


Feedback would be most appreciated.

[cartoonz]

Exactly which PCV valve did you bypass? The one on the driver side is the one that would affect the passenger side bank. If that isnt it, and you already did the valve seals properly, there's only one other way for oil to get into the combustion chamber... and you dont want to go there.

[clubE31]

Could be cilinder/piston or valve seals.

p.s. don't drive it ! It will clog your cat (expensive).

[Belgiumbarry]

cilinder/piston problem is possible , but it is unlikely that all 6 on that bank have it … no ?

[Timm]

I'm sure you know (after all that work) that compression and leak-down tests are needed next!

[aramis001]

I'm sure you know (after all that work) that compression and leak-down tests are needed next!

Thank you for all the feedback.
I worked the PCV on both sides. I just cleaned them again and reinstalled them.


we just did the coolant emission test and the car passed.. so not the gasket/s.

I noticed a slight blow back then followed immediately by a vacuum when oil fill cap was removed. Not sure what that means..

as far as compression test.. we did the compression test and all 12 cylinders are running between 180-182.. Not done the leak-down test yet... I have to educate myself on how to do it.

I am rather hesitant to believe blow by on one bank and all cylinders simultaneously... but who knows..

feedback welcomed

[Timm]

Yes, it sounds very unlikely, especially as your compression values are good and even. It also seems strange that you passed emissions - with oil burning you would expect high hydrocarbon levels. Possibly the problem IS the crankcase ventilation system - but the short test was insufficient to burn the oil from the cats which would be seen as fresh oil burning.....

[shogun]

Cleaning the VCV does sometimes not help, I know from own experience. Years ago I had high oil consumption on the M70, cleaned the VCV system, nothing changed, then I installed a selfmade oil catcher, see here
http://twrite.org/shogunnew/upgrades...or_Shoguns_M70 there I could see that I catched oil. Replaced the parts and no more oil consumption.
http://bmwe32.masscom.net/sean750/vc.../VCVvalves.htm in this link you can also see that they modified once the VCV version
I installed then:
11 15 1 720 392 vacuum hose left 1
11 15 1 720 393 vacuum hose right 1
11 15 1 720 131 non return valve 2
11 15 1 718 642 2 stage valve left 1
11 15 1 718 713 2 stage valve right 1
11 61 1 708 475 DK paper gaskets 2

here another DIY http://www.ow.no/index.php?option=co...d=23&Itemid=13

[aramis001]

Shogan. I followed your other posts in the past.. good work and very informative.
Thank you for the tip on the oil catcher. We tried the oil catcher in the past (using a Jar first, then using a PVC tube). It did in fact helped to reduce the burn, but not the overall oil loss, since all the oil cough in the oil catcher was essentially reduced from my oil pan and i didn't want to put it back in the engine since it was also absorbing moisture from the air. The good thing about it was reduction in the amount of oil burned in the cylinders.. is the piping yuo showed in the links ending inside a tube or Jar or releasing into the atmosphere?

[aramis001]

Yes, it sounds very unlikely, especially as your compression values are good and even. It also seems strange that you passed emissions - with oil burning you would expect high hydrocarbon levels. Possibly the problem IS the crankcase ventilation system - but the short test was insufficient to burn the oil from the cats which would be seen as fresh oil burning.....

Update on leak down test....

note that i just numbered the cylinders as they sit next to each other and am not going by the engines firing order. Cylinder 1-6 are on the passenger side and the bank with the oil burn

1: Cylinder Compression test:
- Cylinder 1 at 160, all other cylinders at 180 (this is a change from last test which was in 2016 . at that time, all cylinders were at 180. (Note that I did have oil loss at that time as well)

2- Leak-down test (used Pittsburgh tester. 10-40% was indicated as "low" on the tester. 40%-60% as Moderate and 80% and up as High)

Bad side (with oil burn)
Cyl 1: 20%
Cyl 2: 20%
Cyl 3: 15%
Cyl 4: 23%
Cyl 5: 25% (ironically this was the cleanest cylinder in the is bank!!)
Cyl 6: 20%


Good side
Cyl 7: 23%
Cyl 8: 15%
Cyl 9: 15%
Cyl 10: 15%
Cyl 11: 15%
Cyl 12: 16%

we repeated the test 2-3 times per each cylinder.

Control- update:
- removed the throttle housing from intake manifold and cleaned the oil from inside both manifolds.
- Removed PCV and the 2ndary and cleaned and tested for flow/ block. They all seem in working order.
- Reinstalled PCV, but, disconnected PCV from valve cover to eliminate any chance for oil vapor into the manifold.


will drive for few days and check oil level, then perhaps remove the throttle housing again and check inside the manifolds to see if any oil... now... if there is oil in the manifold at that time, then i will be completely blown away!!!

will provide an update in few days. In the meantime, feedback on leak-down test welcomed.

[shogun]

.....piping you showed in the links ending inside a tube or Jar or releasing into the atmosphere?

That is normal connected as usual, the oil trap is the large bend in the hose, air will go thru to the other side of the bend, oil will stay in the elbow http://twrite.org/shogunnew/files/pc...m/pcvnew04.jpg
One of my wrenching buddies also made this version of oil catcher http://www.bimmerboard.com/forums/posts/142345/
based on this version made on the German forum http://www.7-forum.com/forum/showthr...?t=52036&page=
Here is a large jar Patrick made for testing, the oil stays in the jar, the air goes in/out on top http:///produkte.bilder-speicher.de/...tcher-m70.html

[cartoonz]

there's also the possibility that one of your cats is melted/blocked, causing serious back pressure. This tends to pressurize the crankcase and overrun the PCV's... if you install catch cans and bypass the PCV's completely, you'll know if this is happening because they will fill up with oil pretty fast. I ran into this issue on my 6 liter engine. Still built a new engine, but looking back on it I would have tried new cats first... as one was wasted

[aramis001]

Update on leak down test....

note that i just numbered the cylinders as they sit next to each other and am not going by the engines firing order. Cylinder 1-6 are on the passenger side and the bank with the oil burn

1: Cylinder Compression test:
- Cylinder 1 at 160, all other cylinders at 180 (this is a change from last test which was in 2016 . at that time, all cylinders were at 180. (Note that I did have oil loss at that time as well)

2- Leak-down test (used Pittsburgh tester. 10-40% was indicated as "low" on the tester. 40%-60% as Moderate and 80% and up as High)

Bad side (with oil burn)
Cyl 1: 20%
Cyl 2: 20%
Cyl 3: 15%
Cyl 4: 23%
Cyl 5: 25% (ironically this was the cleanest cylinder in the is bank!!)
Cyl 6: 20%


Good side
Cyl 7: 23%
Cyl 8: 15%
Cyl 9: 15%
Cyl 10: 15%
Cyl 11: 15%
Cyl 12: 16%

we repeated the test 2-3 times per each cylinder.

Control- update:
- removed the throttle housing from intake manifold and cleaned the oil from inside both manifolds.
- Removed PCV and the 2ndary and cleaned and tested for flow/ block. They all seem in working order.
- Reinstalled PCV, but, disconnected PCV from valve cover to eliminate any chance for oil vapor into the manifold.


will drive for few days and check oil level, then perhaps remove the throttle housing again and check inside the manifolds to see if any oil... now... if there is oil in the manifold at that time, then i will be completely blown away!!!

will provide an update in few days. In the meantime, feedback on leak-down test welcomed.

[Albert850i]

there's also the possibility that one of your cats is melted/blocked, causing serious back pressure. This tends to pressurize the crankcase and overrun the PCV's... if you install catch cans and bypass the PCV's completely, you'll know if this is happening because they will fill up with oil pretty fast. I ran into this issue on my 6 liter engine. Still built a new engine, but looking back on it I would have tried new cats first... as one was wasted

This is how one of my cats looked inside....
Black (and broken) at the intake side, most likely due to burnt oil.
IMG_6563.jpg

[aramis001]

This is how one of my cats looked inside....
Black (and broken) at the intake side, most likely due to burnt oil.
IMG_6563.jpg

I sure hope that is not the way mine is!!!..

- Does anyone have experience with cat cleaners?

- Do any of the folks the forum have feedback on my leak-down test results (above)?