Re: What is part #39-111-709-29 and 39-111-700-24 (archive)

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I believe I have correctly answered this question before (check archives, but could be another board). The BMW 750il does NOT have PCV valves! What it does have is a check valve located at the air boot. The check valve prevents air from being sucked into the crankcase when under vacuum conditions, but will allow pressure to be "recycled" into the combustion chambers when the crankcase is pressurized (i.e. full throttle, blowby conditions).

The apperatus stuck in the grommet in the valve cover is no more than a fitting. It's sole function is to allow two different hoses to be connected to one opening in the valve cover. The hose connected to the bottom of the DK motor assembly is where the crankcase vacuum comes from. The other hose is connected to the check valve.

So, the moral of the story is that when some people say that plugged PCV valves cause excessive pressure in the crankcase which causes oil leaks...they really do not know what they are talking about other than I guess it is possible that a check valve will stick closed (but both at the same time? Again, possible, but not likely).

Here is the conversation we had earlier on the board about PCV Valves (Positive Crankcase Ventilation valves).

From my local dealer I hear there is no PCV valves on a 1988 750iL.
Then I hear the car has volume control valves that plug into the air intake just to the inside of the air mass flow sensor. They have a little ball inside and if they become plugged you simply remove them, clean them in solvent, and put them back on the car.
Then I hear the car has check valves (pcv) and also volume control valves.
Then I hear the oil separator replaces the need for PCV Valves.

So, does the car have PCV Valves that function like a Ford or GM? Can someone explain how the crankcase is ventilated?

Yes their is something similar to a pvc valve on
the 750's, in fact two. I don't know what BMW's
name is for them, but I believe they serve the same purpose.

They are located under the eml motors on the front
end of the intakes. You will see a hose going to
the valve cover and one going to the hose from the
air cleaner to the eml's.

One test to make sure they are working is to take
off the oil filler cap and see if there is a vacuum, which I am told their should, per a BMW
mechanic. There are four valves total in the system, and replacement cost is about $100 for the
parts. Or you could try cleaning them with solvent. I believe the eml's have to be taken off
to get to the valves, however I have not done this
myself, but will in the next few months.

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You should replace the rubber grommets that seat the valves to the valve covers as they are probably very brittle. You will need the following:

1ea 11151718642 valve for cyl\7-12 side $30.75
1ea 11151718713 valve for cyl\1-6 side $30.75
2ea 11151715844 gasket (called adaptors) $2.25
2ea 11611708475 gaskets for throttle mtr $2.10
2ea 11151720131 check valve $11.41

All of the prices are each and BMW list prices. Euarasian was much cheaper. The throttle motor gaskets are cheap insurance to have on in case you damage them when removing throttle motors. You might also consider replacing the 2 air boots for about $21 each. If they are original they will be very brittle.

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I should hope so- I recently paid about $AU200 to have them replaced on my dealer's advice. So if my 750iL does not actually have them, I have just been ripped off!

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Here is the part numbers I was given for the PCV Valves - could some one look these parts up please?

Funny how three days prior to this when I was changing my oil there was so much vacuum in the crankcase I broke my oil filler cap getting it off. Then I go through emissions and fail at idle pass at a high rev. Then two BMW repair shops say every things is working fine when it was there and then another repair shop said that my PCV Valves are clogged and they have contaminated the mass air flow sensor that according to BMW is self cleaning. Which still did not lean the engine out at idle.

Man I hate it when I hear three different stories and pay over $2,000 to the best one.

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Here in Australia the part number on my docket is:
11151720131 (at about $AU 35 each).

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