So after looking around for a long time, I finally bought a 318is a couple of weeks ago. It's a '92 with almost 180k miles, but in really nice shape and has been treated well. I really love the car, it's a lot of fun to drive and even the acceleration is better than I expected given the size of it's engine. The best thing: it's a manual!
Anyways, so two days ago I was dropping of a friend and we ended up talking for about 15 minutes in the car while the engine was idling, and suddenly I realized that the temperature gauge had gone way up and the warning light came on. I shut off the engine immediately and opened the hood, and I saw a little steam coming from the radiator cap. I left the hood open for another 10-15 minutes for the engine to cool down, and finally drove home (which wasn't far) without any problems. What surprised me though was that I couldn't hear the fan running -- I will have to get that checked out.
However, while driving home from work today I noticed that the temperature was going up again -- so far, the gauge usually had always been right in the center, now it was on the line between the center and the red. When traffic was slowing to a stop-and-go, the meter started inching closer to the red, and I was prepared to pull over to the right and stop, but as soon as traffic got lighter and I could drive faster, the meter went back to it's previous place (halfway to red).
Now this really surprised me -- if it's really just a broken fan, when I drive at freeway speeds in "cold" weather (about 65 F), shouldn't the temperature be fine?
The only thing I've done to the car since I bought it was getting an oil change (that was about 2 weeks ago). Unfortunately, I forgot to tell the mechanic what oil it was running, so he put in a different type (what he said was the manufacturer recommended one for this car). Note, this was at an independent garage that specializes in BMW and Mercedes, and the guy had over 15 years of experience (and excellent reviews online). Unfortunately I can't decipher the oil type on the receipt, I'll call the place tomorrow to find out, but I remember that it was mineral oil, while the previous owner said that only synthetic oil (15W50) had been used in the car for the past few years (there's still 2 bottles in the trunk).
Could this be at all related to the different oil? I do remember reading here that it's not good to switch the type. But I also thought that was only related to the seals. (BTW the mechanic said that the seals on this model aren't designed for synthetic oil and it may have caused some leaks. Actually, he showed me the underside of the car which was kinda oily, and told me to wash it off some time before the next oil change, so that next time he'd hopefully be able to find the leak).