1998 BMW 740 Engine Burns Oil

BEN726966

MEMBER
1998 BMW 740
V8
2WD
AUTOMATIC
14,000 MILES

I have a BMW 740IL that burns oil like mad. It puts a hug black smoke screen out bthe exhaust. I did a compression test and it was good. I unplugged vacum lines and found on twards the back of the motor that when unplugged the problem seemed to of went away. There is no PCV valve listed on the under hood emissions sticker. What would possibly be the cause?

2 Replies

DOCHAGERTY

MECHANIC
9,601 POSTS

The plate bolted to the rear of the intake manifold is the PCV valve. It may require replacement. 11-61-7-501-563 is the part number and it can be viewed at Realoem. Com

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Sunday, September 13th, 2009 AT 8:16 AM

HEIFETZ17

MEMBER
10 POSTS

The reason this part is so obscure is because it's not a PCV valve, but functions the same as one. BMW doesn't use PCV valves, but instead these components. That rear plate is an oil separator valve.

You have an oil separator in the front of the engine that separates oil and excess unburned gasses. It sends the oil to the oil pan and the gasses back through the intake to be burned off. It's not quite the same as a conventional PCV valve.

When this OSV goes out, you'll get smoke at startup but not usually while driving, as the valve inside closes off when the intake vacuum increases, thus blocking any flow of excess oil. This is why you'll usually only smoke at startup.