Notes/Photos for replacing a 1998 BMW E38 (M62) Oil Separator Valve.

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The OSV valve is a known point of failure for the M62 engine. It's failure causes dramatic symptoms including a check engine light, billows of smoke out the exhaust, rough idle, and howling. Anyone not knowing the simple cause would consider driving the car over a cliff for the insurance. I would consider this as a preventative maintenance procedure at 80,000 miles. Mine failed at 96,000 miles. The alternative to this procedure is a complete manifold removal. That involves painful steps like removing the injector boxes and the water pump. Unless you need to do that because of a leaking manifold gasket or other reason, it can be avoided, or at least postponed by following the OSV R&R procedure below.

Parts needed: (about $100)
1161 7 501 563 Cover
1161 1 729 728 Gasket
1114 1 460 752 Screws (x7) or substitute M6 x 1.0mm x 25mm hex head bolts.

Tools needed:
1/4" hex drive ratchet driver (Home Depot Husky Pro 66604)
T30 tamper-proof Torx 1/4" drive bit
View mirror
Dental pick
Combination Screwdriver (the kind with the slide-out core with bits)
Large needle-nose pliers

First, you cannot do this job without the 1/4" drive and torx bit. There isn't enough room in back to loosen the torx bolts for even a 1/4" square drive ratchet and standard 1/4" square drive torx bit.

Following the photo below, use the large needle-nose to destroy the single-use clamp on the brake hose taking care not to destroy the hose. Twist the hose and pull off and support out of the way. Then using the core of a combo screwdriver with the big flatblade tip, get under the clip holding the metal tube to the cover and pry up to detach it. Then pull off the two vacuum hoses on either side of the top. Unclip the black braid fuel line from the support on the back of the cover and you are ready to remove the torx screws.

Use the 1/4" hex driver w/ torx bit to remove the torx screws. This is a knuckle-buster and requires some dexterity. Have a magnetic extension tool handy to pick up a dropped screw, etc. It is important to use a name brand tamper-proof bit because it has a better "bite" on the screwheads than the conventional torx bits. The conventional ones have a dome at the tip that works on clean screws, but keeps the tip from going all the way in if there is any dirt. Also, press down into the screw hard while cracking them loose. You do not want to strip one. It is a good idea to get a new set of screws, or even to switch to grade 8 or stainless hex cap bolts or allen bolts which are harder to strip (f*ckn torx strip easily if you are not careful). Then pull the cover backwards and off. Use the dental pick and mirror to pry out the gasket and remove it. Make sure all center rubber seal is removed from the car because a new one is on the new cover.

I snapped the cap off of my old cover and the problem was obvious. It looked exactly as shown with a split and dislodged gasket and a second dislodged o-ring. In addition, the diaphragm was torn. (See photos below). I think the gaskets in the first photo had been that way for a while. There were no noticeable drivability issues and no check light. The hole in the diaphragm was probably the cause of the check light and smoke and howling.

Okay, put some silicon grease on the seals on the new cover, make sure the floating back plate in the manifold is positioned correctly with a mirror, put the new gasket in, and put the new cover on.

There will be a few smokey starts while the remaining oil clears from the manifold. But everything will soon be back to normal. My check engine light even reset itself.