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I have a 2009 convertible 650i automatic. I was driving for a while yesterday and then I was in a line for a drive-through for about 20 minutes with the car on. The fan came on which to me sounds louder than any other car that I've had in the past but I don't know if this fan is normally supposed to be loud anyway. After a little while I got the error message that shows there. I'm not a mechanic and I'm going to take it to a mechanic, but I wanted to find out if there was anything that I should do in the interim to make sure that nothing happens while I'm getting to the mechanic. Also, what are the things that I should be looking for so that the mechanic doesn't screw me over in some way?
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The trans is cooled by driving down the road with air blowing over it, and by the transmission cooler which is on or part of the radiator. When stopped the aux fan pulls air through the radiator which in turn coils the trans fluid.
you could have a bad temp sensor, the auxiliary cooling fan might not have a stage 2, the cooler lines maybe plugged up, lots of possible causes.
If it does turn out to be the trans was indeed hot I would request a fluid change as heat is the enemy to transmissions.
 

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The thermostat for the transmission could be starting to fail, or either your cooling fan is going bad? The thermostat is not that expensive repair, but the cooling fan is not cheap. The fan can be tested with ISTA, if your mechanic has a copy of it? The fan has 4 different speeds, so I would test it before replacing it.
 

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Current: 2009 E63 650i Coupe, 2009 E92 M3 Past: 2012 F10 535i, 2009 E93 335i vert, 2007 Roush 427r
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Just sitting in a drive-thru line for 20 min with the car in gear the whole time could have made the trans hot enough to pop that message, did you keep it in "Drive"? I had it happen at In & Out in Arizona in a long ass drive-thru line and it was about 95 degrees outside ambient at the time.
 

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Check for debris blocking air flow over the transmission cooler and check the fluid level. Worst case scenario would be a slipping “E” clutch which means overhaul. Because your not getting a transmission mechanical fault the fluid seems likely the cause. Also could be the temperature probe is reading incorrectly.
 

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all of the above, and add to those fluid could be low
 

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Is it possible to put an additional cooler for transmission oil?
Hello Grassjello. Yes, it is possible, but the factory installed transmission cooler is substantial. A second cooler should not be needed. Are you having trouble with your car's transmission oil temperature?
 

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I live in a very hot city in Asia, and traffic is really bad. I think it is safer to keep the oil temperature lower, even just a bit.
 

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If the fluid temp is hotter than normal, start looking at the fluid level, or the Mechatronic Adapter Seal. The fluid should be changed at 50k miles to prevent any damage to the internal seals, even thou BMW says it is lifetime fluid.
 

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If the fluid temp is hotter than normal, start looking at the fluid level, or the Mechatronic Adapter Seal. The fluid should be changed at 50k miles to prevent any damage to the internal seals, even thou BMW says it is lifetime fluid.
Thanks for the suggestion. I did change the fluid and all seals about 5k miles ago.
I cannot see the temperature during driving. I have simple OBD2 scanner and Carly app, both of them cannot see the transmission fluid temperature.
 

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A high end OBD2 diagnostic meter will read the temp, INPA, or ISTA. I would probably suspect the Mechatronic Adapter Seal if you have over 70k miles, & the fluid has not been changed. The adapter usually starts failing between 70k to 100k miles, The seal maintains pressure between the valve body & gearbox. You will usually start getting the gearbox wanring on the IDrive when this starts.
 

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Thank you. I will look up diagnostic meters. do not really want to have a laptop on while driving
Currently, there is no warning and transmission seems fine. Adding a cooler is more for peace of mind.
 

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The cooler is large enough to handle the temps, but it might need cleaning? I think your problem is most likely fluid related, or the adapter seal.
 
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