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      08-27-2016, 10:33 PM   #14
PhaseP
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Drives: 325XI
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The oil separator is bolted on to the manifold, I think two bolts but it has been a while I did this. I do not think you can unbolt it, you can't even see the bolts, but you can try maybe you will be able to.

What it really prevents you from pulling the manifold is the oil return line that goes from the oil separator down to a tube that goes into the oil pan.

There is also a electrical junction box that is bolted to the manifold at the lower side that will prevent you from lifting the manifold up. This junction box is bolted to the manifold with two torx bolts via a sheet metal piece of bracket. You can unbolt these if you remove the power steering reservoir out of the way (just remove it from its mounting place by two undoing two nuts and set it aside.) Some people separate the electrical junction box from the sheet metal bracket, but in my case it wasn't coming off. It is connected by something like barbed inserts and meant to be one time in.
You also need to disconnect the throttle body electrical connection there. You will probably need to disconnect the alternator control cable.
And I would suggest AFTER DISCONNECTING BATTERY, disconnect the alternator positive cable, which provides more movement of the manifold while working there. Alternator plus cable is I think live with battery positive cable, hence you need to disconnect battery otherwise it will spark anywhere it touches.

I think you will have to disconnect an electrical connection that goes to another very small junction near the oil separator that distributes voltage to all the heaters on the oil separator related lines/hoses. You cannot see this also, just need to find by feel and use a thin flat screw driver to pry on side and pull it out. It has a notch on onside that holds in place. Which side? you need to test.

Now coming back to oil return line on the oil separator, that is the biggest hurdle. Disconnecting that oil return line from the separator is not easy simple because there is not much room. The connection type is the same as the hose that comes from the valve cover into the oil separator, the one that is visible on the top, you need to squeeze in two sides and pull out. The Bentley manual says to slide your right hand behind the manifold and squeeze the connection and separate the line. But my hands were neither thin nor flexible enough to do that. You may be more lucky in that.

If you cannot disconnect like that, what I would recommend doing is lift the car up on the driver side, remove the engine plastic cover. Then remove the black square kind of protection plate for the gas lines. Then get a 17 mm crescent wrench and unbolt the oil return tube that goes into the engine oil pan. It has an o-ring seal on it, you may want to buy a new one from dealer.

This tube will turn freely without problem because it is connected to the oil return line but sealed with doubled up O-rings that is kept inside that oil return line connection. Once it is freed up from the oil pan, with all the other oil separator/breather lines and electrical lines disconnected and out of the way you can lift up the whole manifold.

Another option is to disconnect oil return line from the oil return tube that goes into the oil pan. For this you need a 1/2 inch automative line disconnect tool. I used a cheap plastic one from Autozone. You need to push the tool all the way in, and while it is all the way in, pull the connection apart. It may be easier done with two people, one pushes in the tool and holds it, the other pulls the manifold up at the same time which will pull the line up and disconnect.

Someone recommended to push the connection there up by placing a big flat screw driver and hitting it with a hammer, which it was reported to him the dealer mechanics are disconnected it this way.

I suggest looking and studying the related DIY articles on PelicanParts website. Search for E90 intake manifold and oil separator related DIY articles there. They have good pictures that explain. Their recommendation is to break off those oil/breather hoses and just replace with new, since they say they break off by time anyway.

It is a tedious and painful job, just because there is not enough room and all crowded in there.

Also disconnect the oil pressure switch/sensor that goes on the side of the oil filter housing, otherwise you will keep hitting the manifold to its cable and may damage it. Don't forget to plug all you disconnected
I am assuming you already disconnected the oxygen sensor cable(or cables don't remember that well) that goes through one loop of the manifold.

Removing the throttle gives more room to disconnect the junction box under the manifold, but depending on the age of the o-ring that seals the throttle body to the manifold, you may end up needing a new one once removed. Unless you don't need to, which I didn't have to, you should leave it alone.

Good luck, have patience, it is doable.