The driver's window came off the track shortly after I purchased it. Easy fix. I took it to my local BMW certified independent mechanic, and it was just a little plastic piece that slides in the track and connects to the mechanism arm. It was fixed in less than 20 minutes. He keeps a supply of these little plastic guide pieces in his shop, and fixes windows for customers all the time. No problem. I am ready for any further window problems. He said there was a lot of resistance in the window track, likely from accumulated dirt and dust over the years. Cleaning the tracks makes the window slide like new, and will prevent too much pressure on the plastic guides and prevent them from snapping.
One side of the power seat stopped working. My trusty mechanic fixed this, too. He said the cables get stretched after time and lose connection. Again, easy fix. He has devised a way to make a new casing for the cable and it "lasts forever." In fact, BMW America now uses his method. While fixing that cable, he also fixed the electric headrest cable. Since he was already in there (removed the seat), it was only a few more minutes of labor.
There was an oil leak. My trusty mechanic said it is a housing that is attached to the block and somewhat difficult to get to, but $300 later, that is fixed. This car drips absolutely nothing.
When I bought the car in late 2011, it made whirring noises at start-up and when accelerating. Once it heated up, the noise was gone. I knew it was the transmission, so I negotiated the purchase price down to $3,800. I figured this was a great price for a car that was in otherwise beautiful condition, and that sold for $50,000 new. I figured I would chalk up the $3,200 for a re-built transmission as a general maintenance cost, knowing that with proper maintenance I would likely never have to replace it again. My trusty mechanic said people think the tranny is sealed, but it's not. There's a plug for checking/draining/adding fluid. He said a properly maintained tranny has its fluid changed every 50,000 miles and using expensive synthetic (US $30 per qt.) tranny fluid is a must. With proper tranny maintenance, it should easily last 200,000 miles. He also said the new transmission is better than the original.
I absolutely love this car. It is heavy, solid, safe, reliable, fast, smooth, quiet, comfortable and handles extremely well. I didn't buy it for gas mileage. I bought it as a car in which to chauffeur clients while selling real estate. I love driving it, and my clients feel special being escorted in such a beautiful and classy car. It's always a topic of conversation as soon as we all climb in and start our day of touring properties. At 19 MPG around town, the miles I drive are tax-deductible anyway, so it's not a great expense.
This car is in such good shape that I recently had someone offer me $10,000 for it. That would be $3,000 more than what I have into it, but no way. Not for sale. I spent a lot of time finding the right car at a good price, spending time, effort and money bringing it up to like-new mechanical condition, and I did it for a reason: I love the car.
Also, my mechanic told me that this car, like BMWs in general, has a self-regulating engine, meaning if you drive it hard, the engine adjusts itself to be more high performance. If you drive it like a granny, it adjusts itself back down to that again. He said to keep it adjusted to high performance, red line it once a day, most easily done in first gear, and it will remain in high performance mode. Gas mileage will suffer, but it will be fast, fast, fast.
Overall, if you can find an older BMW like this that has been well maintained, and if you are willing to expect that the tranny might need replacement at around 200k miles (mine as early due to lack of maintenance), then you can't go wrong. These cars were very well built. They don't make them like this any more.