Shared Knowledge

"BMW X5 - How to Replace the Oil Separator"

9 September 2008

Updated: 24 September 2008

Updated: 8 March 2010

Summary: On paper, replacement of the oil separator (crankcase ventilation valve (CVV)) on a BMW X5 does not appear difficult but reality is often different than the paper story. If you are just replacing the oil separator and nothing else, then the job is not too difficult but you will need long arms and must be able to work blind, meaning you will not be able to see bolts or hose connections as all are behind the engine. If you replace the 2 large hoses connected to the oil separator as part of oil separator replacement, then job becomes a little more difficult, as again, you will be working blind to get hose clamps off that are in tight spaces behind the engine. Finally, unless you specifically know that the small oil return hose connected to the intake manifold rear cover is defective. I advise against replacing it yourself. Replacement of this small oil return hose is possible but a major hassle. The following provides detail of a full and complete oil separator system replacement to include the infamous small oil return hose.

Why I had to replace oil separator or thought I did: (1) oil leak, which seemed to be coming from oil separator hoses connected to metal oil return pipe running down the side of X5 chassis to oil sump; (2) if car sat for 2 days, upon start up, huge cloud of smoke, which smelled of oil or so my wife said (no problems when car running and no coolant disappearing) and (3) could hear a whistling sound from engine at times indicating a vacuum leak somewhere.

Details provided are for BMW X5, model year 2000, 4.4i or M62 engine with 105,000 miles. Always serviced at dealer and oil changes as prescribed by oil service lamps.

Why I did it myself: recent work done by dealer has not been satisfactory like overfilling oil and upon investigating oil separator replacement costs by dealer, apparently $1000 or more and now having done job, I can see why it would cost a ton.

Crankcase ventilation valve = oil separator

The following image shows the entire oil separator system. I have annotated various parts.

CVV system parts the dealer would replace. Note here that I am 99% sure that to replace the small oil return hose that connects to the bottom of the intake manifold rear cover, the dealer would pull the intake manifold and thus the high cost of CVV replacement. In my opinion, there is a serious design flaw in the intake manifold rear cover design in that the nipple at the bottom of the cover onto which the small oil return hose attaches, points towards the front of the engine and is underneath the intake manifold. If this nipple had been pointed towards the passenger compartment, hose replacement would have been a lot simpler and cheaper.

Where is oil separator located? Remove engine acoustic cover (need Allen wrench to remove cover) and 2 large hoses at rear of engine connect to the oil separator (passenger side rear).

Removing old oil separator. To get to hose clamps on 2 large, visible hoses connected to oil separator, I removed the 10mm hex bolt holding the engine acoustic cover support bracket on the left side (need 10mm socket and drive) and loosened the bolt on the right side and moved the bracket out of the way. Note that in every stinking case, where I had to remove a hose clamp, the clamp was turned so that the screw head was almost impossible to get to with a flat blade screwdriver. With patience and either a 5 or 6mm socket and small driver, I was able to get all hose clamps loose or off. When I reinstalled, I made sure hose clamps where oriented such that tightening or subsequent removal was easy. Note that either mark or otherwise pay attention to which hoses connects to which port on oil separator. Although obvious, the hose connected to the crankcase ventilation port on the end of the driver's below the electrical box running along the top of the engine goes into the bottom port on the oil separator and the hose running from the intake manifold rear cover runs to the top port on the oil separator. Both of my hoses had hose clamps with 6mm heads on them.

The oil separator is bolted into a bracket, which is bolted to the intake manifold rear cover. (2) 10mm bolts are used to mount the oil separator to the bracket. Using a 10mm socket and driver, work your left hand around the left side of the engine and then towards the driver's side until you reach the top oil separator bracket bolt and loosen it. Now using your fingers, extract the bolt and set it aside (if your turn the engine acoustic cover upside down on something soft, the inside of the cover is a good holding place for various bolts and other parts.) Once again, work your left hand around the passenger side of the engine and then forward to the driver's side until you can get to the bottom oil separator bracket bolt. This bolt will be more difficult to get to and can be on with significant torque but you will be able to get it. Remove with fingers. Note: upon removing any bolt or using any tool in behind engine, focus on your hands and do not let tools or bolts slip away. A long magnetic pickup can be useful here sometimes but not always. Also note that for whatever reason, I find I can work blind when I actually close my eyes and visualize what my hands or fingers are feeling.

With the (2) 10mm bolts removed, the oil separator will be loose but as the hose connected to the bottom, which runs over to a oil return metal tube that then goes down to the oil sump, runs through part of the intake manifold casting, you can not simply raise the oil separator up to undo the hose clamp at the bottom. Reaching in from the passenger side of the engine and then moving your hand down at least a foot or so, you will find the metal tube and the oil separator hose and small oil return hose connected to it. In my case, I found that the oil separator hose was connected to the metal tube with a 6mm hose clamp. As I said above, of course this hose clamp was rotated such that it was a bitch getting the 6mm socket onto the head, but I did. Once the hose clamp is loose, pull the hose leading to the oil separator off the metal tube and then push the oil separator towards the passenger side of the engine and lift straight up (the bottom of the oil separator has a significant bend to it and it will not pull straight out.

The image below shows detail of the oil separator and small oil return hose connections to the metal oil return tube. I removed the metal tube for several reasons but does not help getting oil separator hose off the tube.

New oil separator installation (no hoses replaced). Attach the hose at the bottom of the oil separator (6mm wrench or socket to tighten hose clamp) that runs over to the metal tube going down the side of the body to the oil sump. In my case, I replaced this hose and found that the new hose was shorter than the old hose and thus could not push the hose all the way on the bottom of the oil separator like the old hose had been. Suggest that you not push the old hose on the oil separator all the way. Now leaving the hose clamp off the end of the hose going to the metal tube, rotate the oil separator so its head is towards the passenger side front wheel and feed the hose through the opening in the intake manifold casting. As you feed and lower the oil separator, rotate it towards the driver's side. Once the oil separator seems to be in place to be bolted up to the bracket, place the hose clamp over the end of the hose in such a way as to make it easy to tighten once you have pushed the hose onto the metal tube. Making sure the oil separator orientation is correct with its ports pointed towards the front of the engine (don't want a twist in this hose), tighten the hose clamp pretty good as this hose can carry oil and you do not want it to leak. With the oil separator hose connected to the metal tube, move the oil separator to its position against the bracket and insert the bottom 10mm bolt by hand. Tighten it as much as you can by hand. Insert the top 10mm bolt and again tighten by hand. Using socket or wrench, tighten both 10mm bolts. Reconnect large hoses making sure you connect the right hose to the right oil separator port, put acoustic cover support bracket back in place and you are done.

Replacing large hoses. As I said, if the dealer does the oil separator replacement, they are going to replace the 2 large hoses that connect to the oil separator. In my case, I did replace these hoses but after examining the old hoses, not sure I would have really had to. Granted the engine compartment is one hot environment and tough on rubber but I saw no cracks or other defects in my old hoses. Never-the-less, I replaced them and if you want to, here is what you do. To remove the hose that connects to the bottom port of the oil separator, on the driver's side of the engine, reach in with your right hand and at the end of the wiring box you will feel how the hose connects to the engine. This is one tight space and I did have to cut some cable ties and slightly move some stuff out of the way to get to the hose clamp. Once again, the hose clamp head was turned in a very bad way to get either a screw driver or 6mm socket or wrench onto it, but using all defined, I did mange to loosen the hose clamp and to pull the hose off the engine port. Now take the old hose and identify which of the 2 new hoses it matches and mark it. Note that these 2 hoses are not the same size diameter at both ends or so I think I found. They want to go on only one way, so pay attention. The second large hose is connected to a port on the intake manifold rear cover directly below where it disappears behind the engine. Again, a tight spot but with your right hand, you can move down to the hose clamp and one way or another loosen it and pull the hose off the port.

Now taking one of the new hoses, slip the hose clamp over the end to be installed on the engine (not the oil separator) and up out of the way and push the hose over the end of either the intake manifold cover or the crankcase ventilation port. Tighten the clamp. Do the same thing with the other hose. In both cases, make sure the hose is oriented correctly before tightening the hose clamp as you do not want too much of a kink or twist in the hose when you connect the other ends to the oil separator. Connect the hose from the crankcase to the lower port on the new oil separator and then the upper hose. Reinstall the engine acoustic cover and you are done.

Replacing small oil return hose. Nasty, nasty, nasty. In my case, when I removed the oil separator from the engine compartment, I found that the small oil return hose (connects to metal oil return tube) that is supposed to be connected to a nipple on the intake manifold rear cover was, in fact, not connected! I pulled the hose up enough to see that it had broken off somehow and thus had to be replaced (source of my oil leak and engine whistling sound?) But looking at the oil separator parts diagram and where the small oil return hose connected to intake manifold cover, there was just no way to get to the intake manifold rear cover fitting as it is under the intake manifold itself. Upon investigation, I discovered that BMW does in fact, pull the intake manifold off to get to this connection. Crap. Now what to do? More investigation. Intake manifold rear cover. As the small oil return hoses connects to the intake manifold rear cover, why not just remove the cover, connect a new hose and replace the cover? On paper a perfect solution but before I even began, discovered that the rear cover is held to the intake manifold with T30 torx (star) bolts. I hate torx bolts. There are 7 torx bolts holding the rear cover onto the intake manifold and with T30 (size of torx bolts or technically screws) tools of one kind or another (bits, short arm wrenches, small ratchet,, etc. etc.) was able to remove 5 of the 7 with great difficulty as all torx bolts are in behind in cramped quarters, plus all are torqued on pretty well.

But struggle as I might, I was unable to budge the 2 torx bolts at the bottom of the intake manifold rear cover. If the other 5 bolts were in tight spaces, the bottom 2 bolts were in spaces that just did not allow any sort of tool to be used to remove them and I tried and tried over several days. Finally, when I had just about lost hope and was on the brink of putting everything back into place and taking car to dealer or independent to pull intake manifold (certainly I did not want to do this), decided to just try to break the intake manifold rear cover out and see if that gave me room to get the bottom 2 bolts out. Yes, breaking the rear cover out would mean having to replace it but was not sure it was good anyways and if I could get new installed and all working, still significantly cheaper than paying dealer. So I removed the brakes vacuum assist hose that is connected to the fitting on the intake manifold rear cover and then used a large flat blade screw driver inserted right at the seam at the top of the cover and pushed hard straight back towards the passenger compartment. As expected the cover cracked along the bottom seam where the 2 stuck bolts where located.

And what did I discover when I had the broken intake manifold rear cover in hand? The small oil return hose nipple on the cover was completely broken off. How it got broken or when, I am not sure. Perhaps I did it with all my hand movement back behind the engine, but I don't think so. This nipple is up underneath the intake manifold and only by pulling the attached hose very hard at an angle would have snapped the nipple off. SO, the intake manifold cover had to be replace anyways and with most of the cover out of the way, I was able to get at and remove the 2 bottom torx bolts without too much difficulty (was not sure how I was going to replace the bottom bolts once the new cover was in place but would deal somehow). And, reaching into the rear of the intake manifold, I found it to be oily. Don't know for sure, but doubt the inside of the intake manifold should be as oily as mine was (either oil separator and\or intake manifold rear cover failure).

With a new intake manifold cover in hand, I attached my new small oil return hose to the nipple and tightened my hose clamp. I then tried to thread the new small oil return hose under the intake manifold towards the metal oil return tube connection but no matter how I tried, I could not get the new hose to be long enough to connect to the tube! Now I am not sure why BMW would make this hose short or so short as to be under tension between the nipple and the metal tube but it appears to me that that is what they did. Seems like another design flaw to me as sooner or later, either the hose is going to split or rip or the nipple is going to break off. So I decided on a Ron modification to the oil return hose business. I bought another hose from the dealer and used a fitting that allowed me to connect 2 hoses together and run the small oil return hose behind the intake manifold rear cover instead of underneath the intake manifold. As 2 small oil return hoses were too long to be connected directly together, I cut both hoses such that I could connect them and still have some play on getting the joined hose around back and down to the metal oil return tube. Before removing the old small oil return hose, I used my air compressor to make sure the metal oil return tube was not cloggeed. Then with the new small oil return hose in place, I replaced the gasket (new) on the inside of the intake manifold and then proceeded to bolt up the intake manifold rear cover in place but this time, I used 10mm hex bolts (bolt, lock washer and then flat washer). With not a lot of effort, I was able to get 5 of the 7 bolts in place and then the bottom 2. As expected, these turned out to be bears but the one closes to the passenger side of the car did eventually tighten up. The other bottom bolt??? I got it inserted and could even get it to tighten down some but the hex head hit the side of the small pipe coming out of the cover. Maybe it would work anyway. Connected all hoses. etc. etc and looked around engine for tools, etc and then under the car. And there, on the garage floor was a rubber grommet thing that I think I remember being over a port on the inside of the intake manifold rear cover. What! Well, it is all together, why not try it? Car started right up but ran like crap. Ok. Either missing grommet thing or rear cover leaking air or something else. So, removed rear intake manifold cover (minimal time with hex bolts in place) and sure enough, find that rubber grommet that should have been on the inside of the cover was not there, so I push grommet I found on garage floor on fitting and reattached rear cover. This time, decided to not install one bolt at bottom that is hitting small pipe coming out of cover. Perhaps not needed? Don't want to use torx bolt there but if car will not run correctly after grommet installed, will install one torx bolt to get cover tight enough.

Check everything again and start car. Car runs fine. Slowly accelerate it to test and seems ok.

Have now driven 100+ miles and so far, no oil leak and no smoke out the back at startup. Still not convinced it totally fixed.

Update: 24 September 2008. Now have driven > 500 miles and still no smoke and no oil leak.

Update: 8 March 2010. Have now driven 25,000 since oil separator replaced and no problems.