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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 7 Series / 8 Series > 7 Series - E38 (1995 - 2001)

7 Series - E38 (1995 - 2001)

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  #1  
Old 06-11-2013, 08:17 PM
lamarselby lamarselby is offline
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smoke..and then there was none

ok...when i first bought the 740il...almost everytime at startup and cloud of smoke would come from the exaust. so, after ordering a osv from amazon(it hasnt arrived yet) it doesnt smoke anymore...at least it hasnt for the last 5 days. is that normal?
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  #2  
Old 06-11-2013, 08:36 PM
Mayorchuck Mayorchuck is offline
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It's possible the membrane is just slightly torn. I would go ahead and change it if you have the part coming. JMO
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  #3  
Old 06-11-2013, 08:39 PM
lamarselby lamarselby is offline
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ok..thnx mayor!
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  #4  
Old 07-14-2013, 08:28 PM
Podmore Podmore is offline
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Quote:
Originally Posted by lamarselby View Post
ok...when i first bought the 740il...almost everytime at startup and cloud of smoke would come from the exaust. so, after ordering a osv from amazon(it hasnt arrived yet) it doesnt smoke anymore...at least it hasnt for the last 5 days. is that normal?
Had a mate who bought a clunker (Ford Granada) while we were on a 12 month course in the UK. Thing used to blow smoke like Cheech and Chong at a frat party. One day he told me happily that the smoking had stopped all by itself. The next day the engine seized from lack of oil .....

Checked your oil level lately?
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  #5  
Old 07-14-2013, 08:51 PM
First740il First740il is offline
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Re: smoke..and then there was none

Do you highway drive at all. I have a 2000 with 166xxx. Mine did the same after highway driving. I run my car hard. If it has not been put in to high rpm for a long time crap can build up. You could very well be burning it off. That's what my Indy BMW mechanic thinks.

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  #6  
Old 07-14-2013, 08:57 PM
lamarselby lamarselby is offline
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yes..i do alot of highway driving..thnx for the input.
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  #7  
Old 07-14-2013, 09:46 PM
Podmore Podmore is offline
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Quote:
Originally Posted by First740il View Post
Do you highway drive at all. I have a 2000 with 166xxx. Mine did the same after highway driving. I run my car hard. If it has not been put in to high rpm for a long time crap can build up. You could very well be burning it off. That's what my Indy BMW mechanic thinks.

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Although it is true that sustained high speed running will often burn off 'crap' (aka carbon deposits) on the cylinder heads and valves, carbon deposits will not produce a cloud of smoke on start up. Burning oil produces this smoke (and burning oil in turn leads to the carbon build-up) - the question is where is the oil coming from? Was it deposited into the cylinder from leaking valve stem seals, is it being sucked up past worn piston rings, or is it being drawn in throught the OSV?

OSVs are not inherently self-healing, and neither are worn valve stem seals or piston rings.

It's possible that if the car had not been driven much before you bought it, the valve stem seals had hardened up causing them to leak; with regular driving and exposure to hot oil, they may be a little softer and able to seal a bit better, thus reducing the amount of oil leaking into the cylinders.

But ... when the smoking stops, check the oil ....
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  #8  
Old 07-14-2013, 10:30 PM
lamarselby lamarselby is offline
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i had my oil changed a few days ago..switched from 5w40 full synthetic to 5w30 conventional. prior to switching..i would leave a trail of smoke(embarrising) from miles on end. but going to 5w30...the smoke(contrail as it would seem like..lol) has all but disappeared and my car drives better. is this normal?
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  #9  
Old 07-14-2013, 10:57 PM
Podmore Podmore is offline
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The slightly thicker / heavier grade oil may possibly be contributing to the reduction in smoke. However now that you mention a significant amount of smoke when running (not just at start-up), let's delve into that a little more:

Did the smoking increase signficantly when you back off the throttle? If so, it's valve stem seals.

Did the smoking increase significantly under acceleration? If so, it's piston rings (do a compression test to check).

If the smoking was pretty much the same under both acceleration and deceleration, then it's the OSV. The dipstick test should confirm this.
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  #10  
Old 07-15-2013, 07:38 AM
lamarselby lamarselby is offline
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The smoke was steady at idle and acceleration. But now that I've switched oils, it only smokes at startup..after that, no more embarrassing contrails.
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