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Oil Separator DIY

When I went to do this, I couldn't find a good DIY. So I wrote this. Enjoy.

Parts Required:
-Oil Separator
-4 hoses which connect to O.S. (1 down to dipstick, 1 to the valve cover, 1 to the forward end of the intake manifold, and one to the back end of the intake manifold)
-If you decide to pull the intake manifold, you will probably also need the intake manifold gasket set.
-May need air intake elbow/boot at throttle body (see below)
-May need several feet of vacuum line (see below)
-Assembly lube is real handy; I use a moly-based grease on rubber joints to make them go back together smoothly and retain a good seal.
-Zip lock baggies and a sharpie pen – I always put fasteners in a ziplock baggie, and I label them with a pen, even if it’s intuitively obvious. You never know when you’re going to get called away from the job, and which child is going to go digging through the garage, and what you’ll forget before you get back. Ziplock baggies are a great idea.
-Labels; pen; if you’re into labeling electrical and vacuum connections, this can be a lifesaver. In this engine bay, all of the electricals are keyed, so you can’t put them in the wrong place. A label may act as a “white flag” to make sure you remember to plug it in, however. If you don’t know what it is, just put the same letter on each side of the connection, “Connection A,” for example.

Tools Required:
-Torx bits.
-Metric socket set with a creative combination of extensions and universal joints.

While You’re In There’s:
(A few things you might also do, you know, while you’re in there.)
-ICV – clean, inspect, replace gasket. Carb Cleaner or Brakleen will do just fine; the tech at my local dealer says they normally just replace them, but a simple cleaning is typically all they need. If your idle is a little rough, this could be a related issue.
-Air intake final elbow inspection; if your car is 5 or 6 years old, this elbow is probably failing, and should probably be replaced. When you pull it out, look for cracks in the rubber. If it’s whole and clean, don’t worry about it, but be prepared to replace it if necessary.
-Replace miscellaneous vacuum hoses; there are about 6 dozen different vacuum hoses floating around the engine bay attached in one way or another to the intake manifold. There’s a whole cluster at the back end of the manifold that’s impossible to get to unless you pull the manifold off, and they’ve probably all rotted through. There’s another one that runs down to a canister on the left side of the transmission that’s also probably bad.
-Vacuum line is generic and universal; you can get 10ft of standard vacuum line at your FLAPS for less than you can get it from the dealer.
-Clean all the electrical connections: get some electrical cleaner, dielectric grease, silicon electric lube, or whatever it is you like to put on your electrical connections. You’ll end up disconnecting virtually every sensor on the left side of the engine bay, and you’d be a fool not to have some cleaner/lube standing by to make sure it all goes back together smoothly.
-DISA Valve / Resonator – some people have told stories about these getting dirty and failing. When you pull it out, clean it real good and inspect for smooth motion.

Procedure:
1 – The first process I’ll walk through is the easier one. The overview is that it requires you to be triple-jointed and take some intelligent guesses about where the Torx screws are located on the installed O.S. It is very possible to get to the O.S. and all of it’s hoses without pulling the manifold. It will save you $60 for the intake manifold gasket, as well as the time required to pull the manifold and reinstall it. You won’t need a micro-torque wrench to put the fuel rail and intake manifold back on. You will, however, need to be comfortable working in the tiny space underneath the installed intake manifold. Pulling the intake manifold is about an 8, where doing the O.S. without is maybe a 6 or a 7, imho. Rebuilding an engine is a 10, changing your oil is a 1. The only reason it’s rated that difficult is because of the complexity: there’s a lot of stuff to keep track of, that’s all. Here goes:
A – Pull the air intake assembly all the way down to the throttle.
A1 - The air box is held on with little clips around the edge; just unclip these and pull the top off.
A2 - Carefully remove the air filter (replace if necessary). Remove the two 10mm bolts on the left side of the airbox. Either loosen the hose clamp that holds the MAF in place (the MAF is the sensor just behind the air box, towards the throttle body) or unclip the MAF from the air box.
A3 – Remove the air box; be careful to note how the auxiliary intake is situated; it’s a bit of a trick to get back in place, and it’s a bit easier to reassemble if you’ve remembered how it came out.
A4 – There’s a vacuum connection on the intake elbow; pull it out. Replace the vacuum line if it’s cracked or worn.
A5 – Loosen the hose clamps on the intake boots, remove the entire assembly. I found that it was actually easier to reach the hose clamps all the way down at the throttle body from underneath the car. To do so, of course, you’ll need to raise and securely support the vehicle (jack stands underneath suspension elements work well, but a good quality hydraulic lift will also work; a floor jack will not work.), pull off the splash guard, etc. Inspect the intake boot/elbow for cracks or damage. Mine was heavily worn, which probably caused all kinds of problems.
B – Remove the DISA Valve / Resonator. The brilliant engineers at BMW designed this awesome system that modifies the volume of the air plenum to maximize the efficiency gains provided by producing a standing resonant wave in the intake manifold. The resonator valve is the doo-dad on the left side of the intake manifold, about halfway back, right on top. It’s held in place with a pair of Torx bolts torqued to about 8ft-lbs. You may get confused and think there are 3 bolts holding it (I did), but the third is actually a mounting bolt for the ICV valve, which you may end up removing later anyway, so it’s ok. The valve should come out very easily; it’s only loosely held in place, so don’t force it. It does require a little creative motion to get it out around the box in the left-rear corner of the bay, but it comes out smoothly every time. Don’t force it.
C – Disconnect any electrical connections that look like they’ll be in your way. Go nuts. As you disconnect it, clean it (so the label will stick), then label it. Trust me: this will make your life happier and easier later. Before re-assembly later, be sure to hit each connection with a little silicon electrical lube, or similar.
D – Remove the electrical conduit box. There are three fasteners: two nuts and a bolt. The bolt is real easy and obvious, so is the first nut. I won’t even tell you where those are, it’s so obvious. The third is a bugger. I didn’t believe it existed until after I had seen pictures of it. Seriously. It lives underneath the throttle body, straight back. Reach in there with your fingers and feel around for a 10mm nut, just like the 10mm nut that holds the conduit mount in place above the throttle body. Once the fasteners are removed, it still won’t come completely out – it’s got way too many wires into the engine bay. However, it will allow you access into the internals under the intake manifold.
E – There’s a small vacuum switching valve at the forward end of the intake manifold, underneath the first big tube, on the left side. It’s hooked onto a rubber mount and comes off real easy. Pull that out of the way.
F – Dipstick should go; it’s held in place with a single large bolt and a whole lot of long-term unhappiness. You must understand: oil gets hot, oil gets cold, oil gets dirty, and that dipstick has seen it all. All the way down at the bottom of the dipstick tube is a connection-hose that runs up to the O.S.; assuming you’ve been following my instructions so far, you have the replacement part for this tube, so it’s ok to cut this one to get it off. You’ll likely need to cut it, because it’s even less happy than the dipstick itself. The dipstick has a little O-ring at the bottom, where it goes into the oil sump. It may need replacing.
G – Remove the ICV, if you want. It’s probably dirty, and it probably needs to be cleaned. There’s two Torx bolts that hold the mount in place (right underneath the DISA, and right on top of the throttle body). Remove the mount and pull it out. The only thing holding it on the back-side is a rubber grommet, which may need to be replaced. The only two fasteners holding it in place, though, are those two Torx bolts into the intake manifold.
H – Remove the throttle body. 4 10mm (iirc) bolts, one at each corner. Comes right out, real easy-like. If you have a DME MS 42.0 car, you may now have throttle issues. I don’t understand how your throttle linkage works. Mine is a DME MS 43.0 car, which doesn’t have that whole step about disconnecting and adjusting the throttle cable. Good luck.
I – The O.S. is held in place with two Torx bolts, both of which should now be accessible. Look at your new O.S. to see where the bolts _should_ be. Go by feel. You can do it. There are also several hoses connected to it. The one that goes up and just be broken off, it should be very brittle by now. The one that goes forward to the valve cover can probably also be broken, though if you can disconnect it, more power to you. The one down to the dipstick can be threaded out attached, then disconnected on the outside. You may also have a small vacuum line running from the left side of the O.S. up to the intake manifold. The O.S. will have that port for the vacuum tube whether your intake manifold has a matching port or not; if your intake manifold has no port, then the tube on the O.S. will be plugged with a blanked vacuum tube.

Re-assembly is mostly the reverse of disassembly. Stop and have a beer to think about how you want it to go back together. Put a little assembly lube on the O.S. hoses to make sure they go on real smooth. At least a couple of those can definitely be put on BEFORE it goes in the car. If they don’t make a full connection, you’ll have a vacuum leak and your car will run like dog-pickles. While you’re in there, clean everything you can get your hands on. Clean electrical connections, clean the dripped oil from the old separator, clean the dust of the manifold. Then go to town.

You might find that you can’t get enough room this way, or like you’d really just like to pull off the entire intake manifold just for grits and shiggles. Hey, more power to ya, man. Here’s the second procedure, which assumes that you’ve already done everything from the first procedure.

2 – Removing the intake manifold. This is a bear. You’ll need to have a new gasket set and a torque wrench that’s good for 11ft-lbs (you really want these torqued right), as well as a magnet-on-a-stick, some small screwdrivers, a pair of circlip pliers, and probably some other stuff. I should emphasize the difficulty here: I’ve rebuilt transmissions, I’ve pulled engines from cars with nothing but a floor jack and a socket set by the side of the freeway, I’ve built whole brake and suspension systems from the ground up. But even with all that experience, I dorked this process up twice in a row. If this is your daily driver and you have to drive it tomorrow, and you’re not entirely confident about how this process will work, maybe pulling the manifold isn’t for you tonight. For the few, the brave … here goes:
A – I’m assuming you’ve already removed the cabin air filter box. It’s pretty easy to get off, and if you need my help to remove it, you may not have read the warnings above.
B – I’m also assuming that you’ve removed the engine cover. Again, if this presents any challenge at all, please question your mechanical skill, as this is about to get fairly challenging.
C – On top of the intake manifold, there is a funny little plastic thing held in place with 4 Torx bolts. It’s attached at both ends to breather hoses that go to the O.S. If you’re planning on replacing both of these, just break them and pull the thing off. Otherwise, carefully separate them from the vacuum manifold. They’re fairly straightforward connectors: squeeze both sides to release the catch, then pull. However, they both have high quality German O-rings in place, and they may be fairly stubborn. Be careful, but be forceful. Once those are out, just wiggle it out; if you’ve pull the 4 bolts and the two hoses, it’s now just held in place by its own O-rings.
D – Next are the electrical connections for the fuel injectors. Start at the front of the engine bay, because it’s easier to see what you’re doing. Gain experience as you go back. They’re held in place with little metal clips. I use a small screwdriver to pry one side out, then a second screwdriver to pry it fully off the hook. Set a magnet in place underneath the clip so when you drop it, it doesn’t go all the way down on top of the engine. If you do drop it, there’s a flat spot underneath the intake manifold where these things collect; that’s more than likely where it ended up. Pull all six of them very carefully, then remove the wiring conduit for the fuel injectors. (It also has a connection at the front for the VANOS, and another one at the middle for air intake temperature; remove those, too.)
E – If you haven’t already done so, it’s a great idea to remove the B+ terminal on the right side of the engine bay. Don’t forget to tape over it so you don’t short your battery to ground. While you’re at it, the two connectors on top of the fuel rail are the post-cat O2 sensor connectors. They pop right out, as do their clips.
F – Next up is the fuel rail. It’s held in place with 4 bolts and 6 clips. The bolts are 10mm and come right out. The clips pry off neatly with a screwdriver. Again, make sure to have a magnet underneath them so when you drop one it isn’t a disaster.
G – If you have the right tools, it’s a great idea to flush the fuel rail back into the tank before you go any farther. If you were a real mechanic in a real pro shop, you’d have a neat little pressure-supply regulator tool for putting pressure into the schraeder valve at the front of the fuel rail. You’d use that to push the fuel back down the rail into the fuel filter, just like the book says you should do. Since you’re reading this, and not the shop manual, you’re just a guy like me who is doing your own BMW maintenance because you’re a poor sod who can’t afford to take it to the dealer for maintenance. Get some rags ready. Wrap some rags around the schraeder valve, push on the needle. It’ll spray gas. If you have rags in the right spots, you won’t make a big mess. Next, wrap rags around each fuel injector. When you pry the fuel rail off, you’re going to dump gas. Once fully wrapped, pry off the fuel rail: the only thing holding it in place is the fuel injector O-rings. Set it off to the side.
H – You should be just about ready to remove the manifold. There’s a whole bunch of little bitty 11mm intake manifold bolts holding it down. Remove all of them with extreme caution: if you drop one, they’re a bugger to find. Keep a magnet underneath them so you don’t drop them into the abyss. If you do drop them, the dealer has your spares at $.52 each. Or, if you’re desperate, they’re the same size as the nuts that hold the right-side engine cover on. When you go to re-assemble, the torque spec is only 11ft-lbs.
I – One more nut: it’s on the underside of the intake manifold, and you have to get it from the bottom. Looking up from underneath the car, there’s a plastic canister with a vacuum line at either end held in place with a single bolt. Remove that bolt, unplug the vacuum line at the front, set it aside. There are two very obvious-looking nuts right out in the open that look like they might be the intake manifold nut. Neither of those are the one you’re looking for. The intake manifold nut is behind and above the second of the two obvious-looking bolts. If you can see it easily while lying on your back underneath the car, it’s the wrong nut. I pulled out quite a few fasteners before I finally found the one that was actually the right one.
J – I haven’t told you about at least two or three hoses, wires, or electrical connections. This isn’t because I’m a cruel bastage who’s trying to sabotage your car, or because I think it will be a great learning experience for you. It’s because I just plain forgot. If you’re doing this, I’m counting on you to have enough mechanical savvy to notice that the manifold won’t come out with hoses and wires still attached. Due diligence applies here. Take a last look around to make sure you’re clear.
K – Pull the intake manifold. Be careful. It’s not heavy, and shouldn’t take a lot of force. If it does, you’re pulling on something incorrectly. Stop, figure out what’s still holding it, remove the connection, and try again. It may help to have a second set of eyes for this part.
L – When you’re removing the intake manifold gasket, exercise caution: there are loose parts that don’t seem like they should be loose. Pull them out, clean them, but don’t drop them in the engine bay.
M – Don’t forget to put rags in the head to keep foreign material from getting in to your cylinders. It’s also a great idea to seriously clean the gasket seating surface before reassembly.

I think that’s about it. If you have recommended changes to this process, or you have more formal names for parts that I’ve labeled as “doodad,” please provide that feedback so I can correct this. I have a couple of pictures from my own engine bay which I might add when I have time. Otherwise, enjoy. :)

Dan
 

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Excellent write-up, and I appreciate the frankness and warnings of the difficulty.

Having done half of the process myself (up to removing the throttle body), one very helpful task is to remove the plastic firewall between the e-box compartment (rear-left of engine bay) and the intake manifold. It's held together by two visible quarter-turn plastic retainers. It helps in getting easier access to the hose clamps of the lower intake boot going to the throttle body and ICV. Those hose clamps come installed with the screws facing the bottom.
 

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Oil Separator DIY

I – One more nut: it’s on the underside of the intake manifold, and you have to get it from the bottom.
That was the nut holding it!!!!
The Bentely manual does not say anything about that! Or maybe I did not pay too much attention.
Anyway, I just took out the OS by taking out the throtle body and the electrical box next to it.
One thing you will have to do is brake the hoses connected to the OS (two of them) and be very very patient. If you go to www.realoem.com, get a diagram, you will be able to see the hoses attached to it.
 

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First post! Been reading these forums for a while and really got caught up on a lot of things. Also, my first BMW vehicle, gives me jitters after owning Honda products that I beleive are the most relaible out there. Anyways, I noticed mine was seeping and dove right in there and did this. Replaced all hoses while there. Not very difficult, just time consuming. There is really no need to to take the manifold off. I removed the air box all the way and took off the throttle body along with the dipstick. Took me 3 hours to peel everything, hold my mouth right and install the new separator and button everything back up.

The OP really made it simple for me.

Thanks!
 

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Discussion Starter #5
Ah, yes, the plastic firewall at the left-rear -- good call.

Kangman, I spent hours looking for that nut. I'm glad I was able to help you find that d*** thing. :) I'm not certain it's necessary to break the hoses -- should be able to get it out hoses intact, if you're skilled. OTOH, if you have the new hoses in hand, there's nothing wrong with breaking them.

nonford, sorry to hear you have so little faith in these cars. ;) I was raised in Hondas and Toyotas, and find working on a Bimmer to be a breath of fresh air ... though I am a little disappointed at how short some of the replacement intervals are. I'm glad you found this to be easy, and especially glad that my write-up was helpful to you. :)

Cheers,
Dan
 

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Thanks for the write up DJ. I refered to it several times during a recent upgrade to all cold weather components.
The reduced space because of the insulated parts made the connection of the 3 hose tough, but other than that, the write up made the job much easier.
 

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Thank you so much! I put my car in the garage this weekend to change the water pump, thermostat, and evaluate how hard it was going to be to change the oil separator. i was not looking forward to taking the intake off, and couldn't find any good posts or DIYs out there on the process, so i was kind of holding back about doing it myself, but this post is awesome! great walk through, i can't wait get my hands dirty with this info. thanks a million1
 

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Great write up and thanks for sharing ... I just love DIY :)
 

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REALLY! Gee I never heard of that!

Again, how about the parts and their respective part numbers associated with the DIY.
obviously you haven't read realoem then, part #'s are there
it's pretty common sense, oil separator, vent hoses, not much else, look at the pix lol
 

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Discussion Starter #16
Alright, because so many people are asking about the part numbers, I'll walk you through the realoem process here. For my car, I'm selecting E46, Sedan, 330i, and the date my car was manufactured. You'll have to select the appropriate options for your car, which may yield different part numbers.

The OS parts are under Engine|Cylinder Head|Crankcase Ventilation Separator. That will take you to: http://www.realoem.com/bmw/showparts.do?model=AV53&mospid=47725&btnr=11_2194&hg=11&fg=15

For this job, you'll need parts 1, 2, 3, 4, and 7. You may also need 6, if your car is so equipped. The part numbers are on the page linked above, so I won't copy and paste them here.

Hope that helps.

Dan
 

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Cool, thanks!! Couple questions...

I've had a random stalling at lower RPM problem (01 330ci 132k) through out the life of my car. So I'm going to replace the OS and all the tubes. I've got everything apart and I'm ready to get the OS out I think. My car has been throwing codes for the throttle assmebly and I'm considering replacing that but will have to read up on that before I do that since I believe there is a special procedure to do that involving electronics. All the intake boots look good but I'll replace anyway along with some of the vacuum lines that I can readily access. I've been somewhat disappointed since there is nothing glaring yet. There is a small tear in the OS tube that runs to the valve cover though and you can see where oil has leaked out at the top there over time. The IDC is a little dirty but moves smoothly back and forth easily when the part is lightly rotated in my hand.

My main quesion is what grease do you recommmend for this job, any in particular? I'd like to pick some up today. Thanks for the help, I hope I can lick this annoying problem tonight or tomorrw. Also are there any pictures or where can I find the diagram of all the vacuum lines that could need replacing. I don't think I'm going to tackle taking the intake manifold off so if it's impossible to attack these lines without doing so I'll not do it.
 

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Discussion Starter #18
Clean the throttle body before you replace it. Those buggers are expensive, and it's possible that a bad OS would allow some back-seepage of oil into the intake manifold, possibly as far up as the throttle body.

The grease that I used was my general purpose moly-based assembly lube automotive grease -- nothing special, just the standard stuff. If you go to your flaps and ask for "moly based assembly lube," you'll get something similar. For this application, the grease isn't essential.

There are no pictures of the vacuum lines, I've looked. I also tried to get some good ones myself, and couldn't manage. It's an awful problem. Sorry.

Good luck, let us know how it goes.

Dan
 

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Thanks for the help. My throttle assy is clean as a whistle really and moves freely. I know they are expensive but I went ahead and bought one hoping that I won't have to dig in there again. I plan on getting back into it tonight, got all the old parts out last night and looked them over. I did break off the little plugged line on the old OS that I need for the new OS. I can't find it though so I'm going to buy something else to serve the purpose then hopefully the install goes well and me breaking the little locking tab on the throttle assy plug doesn't hurt me tooo bad (nothing a couple cleverly placed wire ties can't fix) It so far has been a trying experience but I've been doing OK and hope to have her back together tonight.
 

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Done. What a pain that OS was, wow tricky sucker. Replaced OS and all tubes as well as the throttle body and intake tubes. Realized the dealer didn't bother to replace the o-ring on the oil dipstick tube last time they were in there for the throttle assembly, good work!

Pretty proud, the car started right up so at least I didn't take a step backwards so to speak. As for the stalling and random sputtering we'll have to wait and see how that goes. Thanks for everyones advice along the way.

Here's to a smooth reliable ride!!:thumbsup:
 
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