[PhaseP]

Some pictures of cut away of my old crankcase breather oil separator from my N52 with metal valve cover ('06 model). On the metal valve cover versions, as the one I posted here, this unit is outside of the valve cover tucked inside the intake manifold. In '07 and later year N52's this unit is integrated on the black plastic valve cover. On those plastic valve cover versions, one can see the outside air vent nipple and the shape of the membrane cap on the left back corner of the valve cover. So they work on same principle and pretty much same. Being integrated on the valve cover makes intake manifold removal much easier, and even oil pan replacement easier. The disadvantage, if it goes bad, the whole valve cover needs replacement. Though there is a place that sells repair kit for plastic valve covers, but seems not simple due to the cap being plastic welded to the cover:
https://vanos-bmw.com/valve-cover-n5...mw-11127552281

Now to pictures. This one shows all parts together but cut apart.


Here the outside air vent nipple. When the unit is in good working order, there is no real air flowing from this vent. It is there to make the back side of the valve membrane subject to outside air pressure, and so allows the valve membrane to move up or down with the amount of intake vacuum. On some builds of N52, this vent is connected to another nipple on the intake pipe just before the throttle body via a small tube. Mine wasn't. I couldn't find any specific like build date that would tell which engines have this tube or not.


The heater element. Crank case gases include water vapor and oil along with blow by gases that escaped the cylinder rings from combustion. In cold weather with cold engine the water oil mix can freeze and break the thing. The heater element is to prevent this.


The valve membrane with the spring and plastic guide plate.


Another view of the valve membrane with the plastic guide lifted off:


Cutaway of the oil separator cyclone. This works very much like a cyclonic vacuum cleaner. Oil, water and any solid particles coming from crankcase via the valve cover tube are separated from gases by the cyclone and fall down into the oil pan return tube.


Cutaway view with the membrane and spring in place:


A view of the spiral of the cyclone cone of the separator:


As to failure modes of this unit:

- The orange membrane by age can become brittle and tear. If it tears, the intake vacuum will pull outside air through the tear of the membrane and the vent nipple. This will lean the engine since it happens after the MAF sensor. This can be tested while engine is turned off attaching a tube to this nipple (or use the already existing tube if it is of a build that connects this vent to intake tube) and gently blowing on it. It should allow a small amount of air to be blown but not anymore. (Small amount that allows the membrane to move down on center against the spring inside until it bottoms). Trying to blow not gently may tear an otherwise good membrane.

- The membrane center where it works as controlled vacuum valve has dirt accumulated on it preventing it to close on the orifice at high vacuum like idle. This will cause too much vacuum to be pulled from the crankcase, could cause the crankshaft seals to leak or make noise. Opening the oil fill cap would be difficult with the amount of vacuum being pulled.

- The membrane center may get dirty and/or hardened to a degree not as bad as allowing full vacuum on idle to the crankcase, but still more than it should be. This would result some oil not being separated but get into the intake manifold. Increase oil usage. Which seemed to be my issue.

- If the heater unit didn't function, and water/oil mix inside the unit may freeze at cold and expand cracking the unit. This would be similar to tear on the membrane, outside air will be pulled in.

- The oil return line may get blocked, which will cause the separator cyclone and the rest filled with oil and lose its functionality in terms of oil separation. Any oil from crankcase will end up in the intake manifold. The oil return line that is attached to this separator has a check valve ball at its lower end. This could also lose its functionality by sludge. It would be good practice to spray something like electrical cleaner down that oil return line to free the ball at that check valve.(While the line is disconnected from the oil pan, so cleaner doesn't end up at the oil pan). This check valve prevents air pressure coming from the oil pan up to the separator.

For more information on blow-by gases, positive crankcase ventilation Wikipedia has a good article:
https://en.wikipedia.org/wiki/Crankc...ilation_system

[Cuba]

I believe I am having this issue, but mine is an 07 build with the valve built into the cover.

about once a week I'll get a whistling noise at idle along with slightly rough idling when stopped at a stoplight. it happened again this morning and I tried opening the oil cap and I couldn't do it, which is a way to determine if this is causing the noise/idling.

my question is, is there anything I could do to fix this other than change the cover ($350) or do that other DIY which seemed kind of sketchy?

[PhaseP]

I am afraid if it is indeed your problem you will need to buy new valve cover, or try the repair kit those guys are selling that I linked above.

If you have already valve cover gasket leaking, replacing it may not be that bad. New valve cover I think comes with new gaskets.

[Efthreeoh]

OP, thanks for this thread. It is threads like these that make E90 Post one of the best and informative Forums on the Net. This is all excellent information. I've been under consideration for a while now that my oil separator is suspect. The replacement cost for the whole kit of parts is about $300. When replacing my VCG a few months ago I of course cracked the breather hose coming off the valve cover. I was able to perform a decent field repair of it with plans to later replace the entire oil separator.

At 311,000 miles and now with the understanding of the components involved, I think it is time to replace. I noticed a drastic change in oil consumption around the 230,000 mark, which I've never been able to explain otherwise.

Thanks for the posts.

[Taskmaster]

Awesome info in here!

[PhaseP]

Originally Posted by Efthreeoh

. I noticed a drastic change in oil consumption around the 230,000 mark, which I've never been able to explain otherwise.

I replaced both the oil separator and the line that goes to oil pan. This line as I wrote in my post has a ball operated check valve at its end towards oil pan. It may be this check valve not functioning good also causing oil getting into manifold. The old line I had removed wasn't rattling when shaken. It did start rattling after I cleaned its end with electrical cleaner spray and if I blow from oil pan end it closes, blowing from other end lets air go. I used the newly bought one anyway.

Yeah all those lines and the separator is not cheap when added up.
With the added difficulty of replacing the separator, it makes the plastic valve cover more attractive.

[iahawkeye]

Pffft. Until it cracks or warps. Ask me how I know

Someone's mentioned it before but I don't think it's been done... I'd like to snag a used magnesium vc from a junk yard and retrofit it to my 328 which has the the, uh, "cost optimized" version of the n52 which has the plastic vc.

... Should probably comment on the op... I've been wondering what's inside that thing since I snagged a 3stage on ebay. Looks like the float inside an old toilet... Lol.

[PhaseP]

Grass is always greener on the other side.

It is not economically meaningful to retrofit magnesium valve cover onto an plastic valve cover using N52. It will definitely cost more than a new plastic valve cover, it may come close or pass over the price of two new plastic valve covers.

In terms of hours of work, from my experience it is less frustrating work to replace valve cover than replace oil separator. I did a plastic valve cover gasket for a friend, and did replace my oil separator.

Technically one issue would be the heater electrical connector to all those lines that have heater coils on them. I believe some an electrical line from ECU feeds them and ECU turns it on based on temperature. 328's may not (most probably not) have this electrical line.

Even the engine harness is probably different. Plastic valve cover versions have some harness section going right over the valve cover. I don't remember mine has that section, it may be going around the cover.

[iahawkeye]

Interesting. I had the work done since it was under warranty but I want to say a new plastic vc was something like 400.

Sadly I know nothing about wiring/electrical. Maybe someone that does can speak up.

Does the plastic vc not have a heater element? I would think it would but....? Maybe it heats up quick enough since it's integrated.

So I guess then question then would be is the oil separator in the metal vc more reliable?

[PhaseP]

Well, 328 n52 also has the "angle connector" which is heated, so plastic valve covers may also have the heater electrical output from ECU, if it is same one that goes to that angle connector.

I still think it wouldn't be a wise choice.

[RL325xi]

Hi Phase,

I am in the middle replacing my starter 06' 325xi touring 79k . Of course I broke two expensive Breather hoses while I am removing the intake manifold. Waiting for it to arrive.
There is a lot of oil residue in the intake and the breather hose. I decided to spray some engine cleaner into the intake as well as the oil separator and rinsed off with water. It is so clean now.

I used cloth tower to wipe dry and use a hair dryer to blow dry the inside.
Should I concerned if I have damaged my oil separator??

[PhaseP]

I guess you should be fine. If no symptoms, why worry.

[1QuikWS6]

On a N51 engine the valve cover (and hence the integrated crank case breather) should be covered under SULEV extended emissions warranty for free replacement way after standard warranty is up...

[Mtf1]

Originally Posted by 1QuikWS6

On a N51 engine the valve cover (and hence the integrated crank case breather) should be covered under SULEV extended emissions warranty for free replacement way after standard warranty is up...

Hi, this is great news. My valve cover vent system failed and my dealer, told me it is NOT covered under my SULEV extended warranty. Would you be able to direct me as to where I can get this information so I can show my dealer? Thanks very much!

Its NOT covered only the gasket is, completely stupid, I fought with BMW NA with this.

[jfranci3]

Is that nipple, shown above important? Doesn't anyone know if it completely seals the vent or partially seals it? I touched it and it shot across the garage. I have a mystery vac leak now.

[PhaseP]

Originally Posted by jfranci3

Is that nipple, shown above important? Doesn't anyone know if it completely seals the vent or partially seals it? I touched it and it shot across the garage. I have a mystery vac leak now.

That cover on it is just a dust cover to prevent dirt falling in it, it has no other functionality. It doesn't seal anything, neither partially nor fully. The ambient outside air pressure goes through that nipple tube and is found on the back side of the membrane. Other side of the membrane is crankcase pressure all the time.

The tube under the center of the membrane INSIDE is the intake vacuum.
I don't know how much more I can explain, I already did in the original post and pictures.

[jfranci3]

That's what I thought. Will double check to see that hole is working then.

[p.s.]

Is the top portion that has the diaphragm of the oil separator removable on 07+ they are available at a few sites but i couldn't get mine to budge. can it be pulled off with the valve cover on the car?

[jfranci3]

Originally Posted by p.s.

Is the top portion that has the diaphragm of the oil separator removable on 07+ they are available at a few sites but i couldn't get mine to budge. can it be pulled off with the valve cover on the car?

Do you have a huge plastic thing in your intake well?


If its not removable, just do the whole valve cover. The plastic epoxy melted the valve cover and is leaking again. Also, if you’re bellowing smoke, you need to remove the intake and clean it... and then R&R the O2s.

[PhaseP]

Originally Posted by p.s.

Is the top portion that has the diaphragm of the oil separator removable on 07+ they are available at a few sites but i couldn't get mine to budge. can it be pulled off with the valve cover on the car?

No it is not removable. It is permanently glued or ultrasonic welded. You need to pry or cut the old one out if you want to replace just the diaphragm with the ones available. Or replace the valve cover all together.

[dcay]

I wanted to let everyone know that replacing PCV diaphragm on the plastic vc is doable with patience. The diaphragm cap is glued in a thin bead around the outside edge about 1/16" down from the top edge. I first took a razor blade and cut off the cap prongs behind the clips on the vc. Then I attempted to pull it off by drilling and installing 4 lag screws in the cap. This just broke out the center of the cap, so just use sharp 1/4" chisel to cut and break out the center of the cap and remove the diaphragm and spring inside. Then you have to break away the remaining cap out to the sides. Ty to break the cap top off the top of the opening lip t provide access to the side/opening seam for prying.

Start cutting away the sides by scoring/cutting vertical breaks in the side piece between a pair of clips. Cut or pry that piece out and score more break lines on both sides of the clips. Most of the glue bond o the side pieces is broken free by prying gently at the pieces. On mine about 2/3 of the side came loose. The other 1/3 had to be carefully shaved off with the chisel. I had to buy and make a 30 deg bend in a 1/4" chisel with a torch to access and clean up the lower side of the opening.

The replacement PCV caps have a different configuration with the cap following the inside and outside sides of the opening. I just put about 1/8"-3/16" RTV sealant inside the groove on the cap and snapped it onto the vc opening clips.

I think I took about 3 hours to get this done.

dcay
2009 328i