I've had a couple mystery problems on my 2000 540i that I haven't been able to figure out yet; hopefully someone here might know what they are. The first is white smoke on startup. It happens fairly regularly, but very inconsistently, with no discernable correlation with the amount of time the car has been sitting and whether or not it smokes. It rarely smokes first thing in the morning, never smokes if it's been sitting a couple minutes, but almost always smokes when I start it up after work. My mechanic suspects the valve guide seals. The PCV has been replaced, and the smoke did not go away. The second is a creaking sound at low speeds. It can be heard/felt inside the car while rolling at a couple mph (like through a parking lot), but cannot be heard from outside the car. This is also not regular - it doesn't happen all the time, maybe 1-2 times a week. It goes away upon acceleration. Thoughts?
Does it correlate with ambient temperature? Do you have fold-down rear seats? I spent many months intermittently trying to diagnose a creaking noise that seemed to come from the rear suspension during low-speed cornering. I couldn't find it, the dealer couldn't find it, it sounded like something big was moving and was slowly driving me crazy. One day I was cleaning the rear seat area, leaned my weight on the seat back at a funny angle--and heard the creak. Turns out there is a small spring-loaded pin that pops the seat back forward about an inch when you release the catch. It fits into a concavity on the seat back. The pin was sticking and squeaking and the parcel shelf acted like a drumhead, amplifying the sound. I lightly greased the pin, its bore and the concavity on both seat halves and haven't heard a peep (creak) since. If you don't have fold-down seats...well, I hope you enjoyed the story.
Don't have the folding seats (didn't think so, being a TX car), and the creaking did happen while out and about today. I can be rolling 1-2 mph in a straight line and it will make the sound.
I found some answers for you regarding both issues. regarding the white smoke: most seem divided between normal moisture in the system or your valve guide seals are going bad. http://answers.yahoo.com/question/index?qid=20090507101133AAhxKG1 As for the squeak, try this. Get a friend to help you with this. Put the car in neutral and roll it forward WITHOUT sitting in the car. If you or your friend still hear the squeak without sitting in the car, that sounds like it could be your wheel bearings. If you don't, get in the car and roll it forward a little. If you or your friend now hear the squeak, it's either your springs or your front end needs service (possibly control arms or control arm bushings).
I replaced my valve cover gaskets last weekend as they were leaking anyways, and it hasn't smoked in a week. Crossing my fingers that it doesn't come back...
Just an update in case anyone experiences these problems in the future. It's approaching 3 weeks since I replaced the valve cover gaskets, at which time the smoke mysteriously went away and has yet to return. Replacing the thrust arms eliminated the creaking as well as the shaking at 55mph. EDIT: Turns out I spoke too soon - the creaking came back yesterday afternoon.
Finally fixed the creaking by replacing the center link and tie rod ends. Unfortunately, the smoke has returned, which is making it look more like valve guide seals. The thing I don't get is why it would have gone away for 4 months after changing the valve cover gaskets...
Alright, checking in again since it appears this has finally been resolved. Turns out the smoke was being caused by a couple things - a leaking front timing case gasket and oil separator tube (in the intake). Having those replaced/corrected has eliminated the smoke; hopefully this time for good.
