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E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 04-11-2014, 10:04 AM
ilian007 ilian007 is offline
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Question Transmission Cooling Problem

Hello Guys,

It is about time for my new problem. Every month there is something

My transmission is giving me problems in the summer for many years.

last week I just discovered that it is related to the Air condition. When I use it the transmission start overheating and going to safe mode. Even if the weather outside is cool. Without the A/C there are almost 0 problems with the transmission.

I was looking and saw there is a small radiator installed for cooling the transmission fluid. However, it is on the back of the A/C radiator (correct me if I am wrong).

I think to install additional transmission radiator adding it in front of all radiators.

Any suggestions ? Maybe some racing alternatives that already dealt with extra cooling of the transmission ? Thanks !

p.s I am going to replace the Fan Clutch as well because it seems it doesn't work well neither.

2002 E39 530i AT - 170k miles
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  #2  
Old 04-11-2014, 02:25 PM
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bartelbe bartelbe is offline
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You are correct the trans cooler sits in between the radiator and ac condenser. Check to make sure that both coolers aren't clogged with bugs/road debris. Also check the trans fluid level as being to low or overfilled can also cause excessive heat. There should be no need for a aftermaket cooler if one is needed on a stock car then something else is failing internally in the trans and will eventually force you to deal with the true cause.
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Old 08-18-2014, 09:32 AM
ilian007 ilian007 is offline
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Problem Solved after 4-5 Years !

Transmission Was overheating due to bad Engine Cooling Fan Clutch. Not Enough cooling of the Transmission Radiator.
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Old 08-18-2014, 09:34 AM
ilian007 ilian007 is offline
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Too Bad I didn't find earlier that Fan Clutch can cause transmission overheating Many Shops including BMW dealer wanted to replace (rebuilt) the transmission!
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Old 08-18-2014, 09:41 AM
edjack edjack is offline
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You should periodically check the clutch for correct operation. The cooling system is designed such that the fan is required to be working.

Does the aux fan run?

Consider having the trans fluid changed, now that it has overheated. Trans fluid is very sensitive to overtemps, much more so than motor oil, and the life is shortened (probably has never been changed, anyway).
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Last edited by edjack; 08-18-2014 at 09:43 AM.
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Old 08-23-2014, 12:16 PM
ilian007 ilian007 is offline
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Yep the Aux fan works. It stopped at some point as well, but there was code telling me, and I changed it.

Now with the Fan Clutch replaced transmission is much better. I guess I need to replace the fluid because I might overheat it many times.

Thank You
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