XSeries-forum

No other symptoms thus far. Car just under 80k, 2004.

Only time this occurs is if I let idle for several minutes once up to temp, a little stab of accelerator generates a puff of whitish smoke from both banks of exhaust. Needs to idle for a while to repeat symptoms.

This is not typical condensation from exhaust but something that can be reproduced even after a long journey.

Car is due an oil service soon. Have had to top up oil a few times recently. Pretty sure I haven over filled though.

I did run the engine for about 30 secs
Without oil filler cap in place just before noticing this but can't think how that might cause the smoke?

Any ideas? Is this classic air / oil separator problem? Is there anything I can test easily?

Is it steam or smoke, and if smoke what does it smell like?

It's still pretty cold at present so you may get steam production at the tail end of the exhaust as it cools down - and that can happen pretty quickly if it's only a few degrees outside.

Pretty sure it's smoke, has that eerie drift off quality about it, hard to describe exactly what I mean but steam tends to dissipate more quickly than what I have seen.

I need to do a few more tests with the help of a 2nd person and see if I can qualify the prob a bit more I.e exact colour and any associated smell. That might give an idea if it's oil, water or fuel.

This could well be the crankcase breather valves having split diaphragms not uncommon on the N62 engine at this Sort of miles.
Good news is that replacement is cheap and easy . One valve on each cylinder bank under the coil covers , the valves just snap fit to the plastic rocker cover .
I would replace the pair and possibly an oil and filter change and see how it goes . If it still smokes and it's definatly a blue oil smoke could well be valve stem seals / worn guides although this is very rare.
Good luck.

If it's not dissipating I agree that sounds more like smoke than steam....and more likely to be oil as you suspected. Fuel would be black. What's the oil consumption like?

If you have not had the separator(s) changed then that has to be worth doing. There are references to it on Xoutpost. Crankcase breathers seem to be an issue on all the BMW engines - we have to do it on the M57TU diesel too.

+1 on the breathers try them there about £16 from the stealers so worth doing even if its not them!
my 4.8 has this problem was once on the Chelsea embankment in traffic and smoked out the people behind me when i eventually hit the throttle,
on mine it ended up being the intermediate levers? (maybe) i think its something to do with the valve stems.....

Thanks for all the input. I'm sure it's oil smoke now. Had the chance to watch it more closely and smell the odour too.

Sounds like the logical order from here is
1) get the oil service done (which was on the cards anyway)
2) replace the crankcase breather valves (might have a go at this myself)
3) if smoke persists, look into the air / oil separators as potential culprits
4) panic if it is the valve stems / seals!!!

Does anyone have any links to diagrams showing the crank case breather valves and the air / oil separators. Would just give me an idea of what's what, find it difficult to visualise what goes where without diagrams!

Just thinking out loud..... does that fact that the car has to idle for some time when warm and then need a stab of throttle to emit smoke suggest that this is oil in the intake manifold rather than into the pistons via valves? When my air cooled 911 valve stems seals went, it would continually smoke at idle rather than just puff smoke when accelerator pressed after idling.

Where do the crank case vents let the oil go if they fail? Likewise, where does the separator let the oil go that it shouldn't? Wish there was a workshop manual for these cars!!!!

Will feed back the outcome for future reference.

there is a Bentley workshop manual for the 4.4.
Lez

Bentley purchased cheers, hope it makes things clearer, quite expensive!

Just thought I'd mention something regarding the Bentley manual here, don't bother buying it if you have the n62 (rather than m62) engine... there's pretty much sweet FA of relevance in any paragraphs with the most common words being " this chapter does not cover the N62 variant" etc, etc. Bloody useless, wish I hadn't wasted my money! (Lez, not your fault at all by the way, the cover clearly states it is for all models to 2006!!!) Anyone with the pre-facelift wanna make an offer on it???

On the original subject, Oil service done, CCVs changed , smoke is all but gone.

Manual notwithstanding (  :wall: ) it sounds like you've had a bit of a result..

Complete result considering the alternatives... 

Just as a follow up, if anyone else has similar issues, it took a few days and some good driving to clear the smoking after changing the CCV valves.  Not sure exactly why, but I guess once excess oil finds its way into the intake manifold, it takes a while for it to clear even though the root cause is fixed.

Incidentally, whilst I was in for my oil service, BMW suggested "further investigation and stripping down head to diagnose problem" !!!  I didn't get the final price for that bit of 'investigative work', but seeing they added £60 to my bill just to confirm what I'd already told them I could foresee many £000s in charges to be told a new head required!!!!!! Barstewards.

Hmm.....obviously touting for work.  No wonder people don't trust Dealers!!