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What are the symptoms of a failed OSV?

25K views 4 replies 3 participants last post by  marti5 
#1 ·
I am trying to assess if my 2000 740iL OSV is gone, or at least on its way to failing. I have read that if you remove the Engine Oil dipstick that there will be minor vacuum down the dipstick tube, the idle may change or become rough.

My car does have these symptoms. If I place my finger over the top of the tube, I can feel a minor suction, but not anything like what you'd call strong. If I rapidly remove my finger from the dipstick tube, there is a clearly audible sound (from the rear of the motor) like a spring loaded valve acting.

Does a failed OSV also contribute towards premature gasket failure on the rocker covers resulting in oil leaks around the covers?

 
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#3 ·
If I place my finger over the top of the tube, I can feel a minor suction, but not anything like what you'd call strong. If I rapidly remove my finger from the dipstick tube, there is a clearly audible sound (from the rear of the motor) like a spring loaded valve acting.

Does a failed OSV also contribute towards premature gasket failure on the rocker covers resulting in oil leaks around the covers?

So is the first observation (dip stick suction) above normal or an indicator of a failing OSV ?

Is there any connection between the OSV failing and rocker cover gasket oil leaks?
 
#4 ·
Sorry, I should have quoted a bit from the story, you need to click that link to take you to the story and the detailed repair instructions... :) But yes, that is absolutely one of the symptoms. When mine went I couldn't figure out what the sucking noise was until I read about the problem.

"Let me explain what I experienced. I had a bit of a squeal, almost like belt chatter, so I sprayed some belt conditioner on the belts but this did not cure the problem. Then my SES light came on and I read code P1159 and P1161. These codes are actually for the O2 Sensors, but I pulled the dipstick and the air was just rushing in and the idle changed a little. This is NOT normal, so I started with the Rear Manifold Cover and will see what I get."
...read more...

Here is the link again if it doesn't come through:
Rear Manifold Cover aka. OSV | BMW 740iL | Magnum
 
#5 · (Edited)
PCV Valve Failure. The V8 E38's suffer from PCV valve failure when they reach a certain age. The PCV valve consists of a diaphragm fitted to a housing that is fitted to the rear of the inlet manifold and when this is damaged it can cause erratic idling and excess smoke. Often mistaken for Nikasil problems in the early models, the repair is pretty straight-forward but does require a bit of patience especially when trying to get the Torx bolts out of the bellows assembly.

The biggest give away is clouds of smoke from the rear on start up,which dissipates after a minute or so, they fail approx 80-110k miles.
 
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