2000 BMW 740 valves

This is actually a very common issue on these cars. There's an oil separator valve (OSV) on the back of the intake manifold. This valve is a common weak point, and when it fails, you'll get smoke upon startup. The valve runs around $75 and some people have been able to replace them without taking the intake manifold off. I just removed the manifold on mine to make it easier.

The second option is the oil separator inside the left timing cover. This isn't as likely the cause, and it's also a fairly major job, as the lower timing cover and timing chain have to be removed.

Thank you - funny thing you mentioned the OSV - is I ordered an oil separator valve yesterday and will be digging into that this week. Hope that is the answer.

Follow up -

I just find this start-up oil smoke too coincidental because It happened immediately after I changed valve cover and timing chain cover gaskets. NO smoke before. Could I have disturbed something of which I was unaware going in there? I must have. The osv doesn't seem to be close enough for me to have damaged.

Chris

The tube from the PCV plate forward has to turn 90° to get to the separator, that's where the break is.

Dr. Haggerty

I know this sounds dumb form someone who just changed the valve covers water pump, radiator and serp belts - but You said "The tube from the PCV plate forward has to turn 90° to get to the separator, that's where the break is."

I don't recall that. Can you describe it? Are you suggesting it broke somehow and that is likely causing the leak and smoking at start up? Where is it?

Thank you very much in advance...

CMB

That is exactly right. There is a turn at the top of the valve and the drain tube should also be checked for blockage.

https://www.2carpros.com/articles/mitchell1eautorepair-car-repair-manuals

Dr. Haggerty Thanks again -

TWO FOLLOW UP THEN I HOPE NOT TO BOTHER YOU ANYMORE

1 - Is it likely I did this while changing the valve cover and timing cover gaskets? It wasn't smoking before.

2 - I ran the car, removed the oil dip stick, and there seemed to be no suction at the dip stick tube, which I thought was an indication of a bad OSV. Can the OSV cause this smoke with no suction on that test?

Thanks

CMB

1. Yes, that's possibly what happened
2. You have it reversed, no vacuum indicates correct operation, vacuum indicates failure of the crank vent.

There is NO VACUUM when I remove the dip stick while engine runs. I can't feel anything.

Is that an idiot-proof check or could start-up smoke still be a bad OSV even when no vacuum is present?

Is there another way to tell if the OSV is bad?

Getting frustrated in Pensacola