Solved Idle Overheating Issue
Hello all! First time poster here.
About a few weeks ago, I bought a 2001 330xi, manual. It needed some work, and I've been slowly replacing parts here and there to get it back into as pristine condition as I can(replacing valve cover gasket, replacing pulleys that were done with life, etc.). It still needs some work. I have a feeling the previous owner bought the thing and didn't have the money to maintain it.
But the single issue I have been having a hard time was with its overheating. Whenever I would come to a stop, or drive less than 20mph, the A/C would shut off and just blow outside (and humid) air. Shortly after that (maybe 20 seconds) I would notice the temperature gauge start to creep to the right. I basically narrowed it down to the fan not blowing air when this happened, but it was like as soon as the a/c shut off, that's when the electric fan stopped. I scoured over these forums trying to find a solution, but the threads that were similar or the same as mine never had final solutions to them, just suggestions.
Well, I replaced as much of the cooling system as possible, minus the radiator. I've bled, rebled, and rebled the coolant a million times. The one thing I thought would have worked was the coolant temperature sensor, my thinking being that it wasn't sending proper temperatures and therefore the fan wouldn't turn on. That sensor was stuck in the lower hose, so I ended up having to get a new one. But, no it didn't work.
I decided after this, the last thing that could have been wrong was the electric fan. Every post about its relay was saying that it was built into the fan, so the whole thing had to be replaced.
I just received the fan, swapped it out with the old one, and took the car for a short drive, and let it idle for about 15 minutes. AND IT WORKED! No more overheating! The fan stays on, the a/c hasn't cut out at all. Usually at 1pm here in Texas, it barely went a minute or two idle before the a/c cut out and the temperature gauge creeped right.
I wish I would have just swapped it out in the first place, but I was trying to replace the cheaper things first, or more likely things. I never knew the old fan was going bad(though it is very old, there is rust on it).
So for anyone having this issue, if you're having these symptoms, definitely try the cooling system, but replacing the fan worked for me!
My idea as to why this is happening: the new fan blows noticeably more air when it is on. This leads me to believe that the old fan was on its last legs. When idling, it couldn't keep up with the cooling demand, and perhaps that's why the a/c would shut off, because it wasn't being cooled? And of course, with nothing blowing through the radiator, obviously the engine temperatures would rise. I could be very wrong here, any corrections are welcome!
Thanks for reading, hope I have contributed something. These forums have helped me out a lot.