Lots of cars getting up in there in mileage now (mine is 82K), so adding some more info. My car is in the shop at the moment, undrivable due to engine overtemp warnings coming up repeatedly (after a week of leaving my car garaged).
AUTOMATIC TRANSMISSION FLUID LEAK:
I'll start off with the ATF fluid (ZF 6HP19). As there are many threads on this already, I'll keep it short. Basically, noticed transmission oil leaked after a week of non-use, and confirmed after my car was put on a lift at the mechanic's. Interesting that others also noticed leaks after leaving their car parked for an extended period of time. Search for the SIB if you're still under warranty.
Luckily, I already ordered the following kit months ago in preparation of my next track event:
http://www.thectsc.com/index.php?p=p...=187&parent=43
$238.03 + shipping
Labor was 1.75 hrs for me.
Lastly, my oil came out black, so if you track your car, this is a MUST do maintenance!
IMPORTANT: 6 liters included in the kit is NOT enough if you're doing a thorough drain. My car was left to drain overnight. I recommend purchasing an extra 2-3 liters at $17.13 from the site. I had to pay $30/liter locally because I didn't stock enough.
ENGINE OVERTEMP (Coolant Temp):
The primary reason for my car being undrivable is due to an engine overtemp warning. I went into the diagnostics settings in the cluster to monitor my water temps (see this thread if you want to know how):
http://www.e90post.com/forums/showthread.php?t=412156
What I saw was that as soon as I started driving the car, the water temps would increase by 1 deg C every sec until it reached 120C, upon which the yellow overtemp warning would pop up. <30 secs later, it would turn to RED, thereby eliminating all power to car, requiring me to coast to the side of the freeway and stop.
After restarting the car, the water temps would read 69C, and would once again proceed to increase at 1 deg C per sec until same error occurs. I can hear the fan running at max speed the entire time.
At the mechanic, my car was placed on a lift and inspected. When the cover was removed, immediately saw coolant leaks on the left and right side. Also, my intercooler had obvious signs of coolant leaks. Engine was NOT hot. In fact, my mechanic even opened the coolant cap, and the coolant was still full. I even placed my hands on the plastic engine cover, and it was cool. It's currently 40F in the mornings, in the Bay Area.
BT SCAN revealed these codes:
2E82 Elctrical cooling pump: switch off
2E8E Intelligent battery sensor, communication
2E81 Elctrical cooling pump:, speed deviation
Before leaving for the shop, I tested my Electric cooling pump using the bleeding procedure mentioned in the coolant DIY replacement threads (search). I confirmed my electric pump was working.
At this point, my mechanic mentioned my radiator may be cracked (I will confirm later today). He went ahead and replaced the radiator and some hoses (not sure which).
Unfortunately, the issue is still present. Next step is to change the electric sensor. I will find out later today if this is the solution. My mechanic doesn't believe the thermostat to be the problem. If this doesn't resolve the issue, he believes there may be an electronics issue.
As of now, it's unconfirmed if I actually have a cracked radiator. It may have been a hose issue, which means the radiator replacement may have been an unnecessary expense. To be honest, I'm a little bummed, since I track my car, and could've used the opportunity to investigate an aftermarket radiator alternative. But I am currently carless, and taking public transportation, so the priority is to get the car up and running before Xmas so my holiday plans are not placed in jeopardy.
Since I track my car, I refilled w/ a low ~25% coolant:water ratio, and also added 2 bottles of Motul MoCool along with it. I'm in California, so don't have to worry about freezing conditions. I will post pics when I have time.
Labor: Currently 2.75 hrs for radiator replacement, which obviously includes coolant flush.
Other Facts (if an electrical issue):
A month ago (Nov 2011), I replaced my battery with a Walmart battery. It seems to be working fine, and I did charge my battery overnight and cleared codes before driving to the mechanic. I also inspected my wiring, including the IBS, and everything looks ok. Unfortunately, overtemp error still occurred. Some people theorized that the wrong battery may not be supplying sufficient voltage or current, however battery problem is lower on the probable cause list for now.
Total Cost: >$1K (ouch, hehe)
Will update more later but if you have any similar experiences, or feedback, would appreciate your input.