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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Technical Forums > Mechanical Maintenance: Break-in / Oil & Fluids / Servicing / Warranty > Leaking transmission fluid after replacing pan and fluid - 2006 330i



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      12-26-2020, 07:25 PM   #1
ultimta
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Leaking transmission fluid after replacing pan and fluid - 2006 330i

Hi everyone,
recently my E90 330i has been giving me a massive headache, and I'm hoping one of you might be able to help me solve my problem. About 2 weeks ago I replaced the transmission pan and fluid on the car at around 115k miles. The car drove great after that and the shifting was noticeably better, however over the last few days I've started to notice some decent sized puddles of transmission fluid under the car after it is parked for a few hours. While replacing the pan, I also tightened the bolts for the mechatronic unit until they were snug. I reused the bolts for the pan and also tightened them until snug (I didn't have access to a torch wrench while I was doing this job). I made sure to clean the mating surface of the gasket. The leak has grown over the last few days, and I've noticed that its been leaking more as the temperature has been dropping. My concerns are tracking down the source of the leak. Is it possible that I may have cracked a sleeve by tightening the screws on the mechatronic unit? What are common areas of leakage for the pan? The car did not leak nearly as much fluid if any before replacing the pan. Thank you in advance for your help!
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      12-26-2020, 09:28 PM   #2
Steve Sas
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Recheck the pan bolts to see they haven't gone loose.
Also check the main electrical connector which is a common area that leaks with age.
Maybe moving thinks around caused the seal to start leaking. This is why its best to replace as many seals as possible when doing a transmission service.
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      12-26-2020, 09:31 PM   #3
thomas1097
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Quote:
Originally Posted by ultimta View Post
Hi everyone,
recently my E90 330i has been giving me a massive headache, and I'm hoping one of you might be able to help me solve my problem. About 2 weeks ago I replaced the transmission pan and fluid on the car at around 115k miles. The car drove great after that and the shifting was noticeably better, however over the last few days I've started to notice some decent sized puddles of transmission fluid under the car after it is parked for a few hours. While replacing the pan, I also tightened the bolts for the mechatronic unit until they were snug. I reused the bolts for the pan and also tightened them until snug (I didn't have access to a torch wrench while I was doing this job). I made sure to clean the mating surface of the gasket. The leak has grown over the last few days, and I've noticed that its been leaking more as the temperature has been dropping. My concerns are tracking down the source of the leak. Is it possible that I may have cracked a sleeve by tightening the screws on the mechatronic unit? What are common areas of leakage for the pan? The car did not leak nearly as much fluid if any before replacing the pan. Thank you in advance for your help!
There is a specific order in which you tighten the bolts. You can't just tighten them willy nilly one after the other. It's like a cross sectioning pattern you have to follow
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      12-26-2020, 10:03 PM   #4
ultimta
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Quote:
Originally Posted by Steve Sas View Post
Recheck the pan bolts to see they haven't gone loose.
Also check the main electrical connector which is a common area that leaks with age.
Maybe moving thinks around caused the seal to start leaking. This is why its best to replace as many seals as possible when doing a transmission service.
Thanks, I'll take a look at them tomorrow morning. I have noticed that the electrical connector is usually covered in fluid so it's likely that it is in fact leaking from there as well. I think I may be redoing the job and replacing all the seals to be safe.

Quote:
Originally Posted by thomas1097 View Post
There is a specific order in which you tighten the bolts. You can't just tighten them willy nilly one after the other. It's like a cross sectioning pattern you have to follow
I did follow the torque order, however I didn't have a torque wrench at the time. Is it possible to cause damage to the gasket by over torqueing the bolts?
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      12-26-2020, 10:31 PM   #5
thomas1097
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Quote:
Originally Posted by ultimta View Post
Quote:
Originally Posted by Steve Sas View Post
Recheck the pan bolts to see they haven't gone loose.
Also check the main electrical connector which is a common area that leaks with age.
Maybe moving thinks around caused the seal to start leaking. This is why its best to replace as many seals as possible when doing a transmission service.
Thanks, I'll take a look at them tomorrow morning. I have noticed that the electrical connector is usually covered in fluid so it's likely that it is in fact leaking from there as well. I think I may be redoing the job and replacing all the seals to be safe.

Quote:
Originally Posted by thomas1097 View Post
There is a specific order in which you tighten the bolts. You can't just tighten them willy nilly one after the other. It's like a cross sectioning pattern you have to follow
I did follow the torque order, however I didn't have a torque wrench at the time. Is it possible to cause damage to the gasket by over torqueing the bolts?
Quote:
Originally Posted by ultimta View Post
Quote:
Originally Posted by Steve Sas View Post
Recheck the pan bolts to see they haven't gone loose.
Also check the main electrical connector which is a common area that leaks with age.
Maybe moving thinks around caused the seal to start leaking. This is why its best to replace as many seals as possible when doing a transmission service.
Thanks, I'll take a look at them tomorrow morning. I have noticed that the electrical connector is usually covered in fluid so it's likely that it is in fact leaking from there as well. I think I may be redoing the job and replacing all the seals to be safe.

Quote:
Originally Posted by thomas1097 View Post
There is a specific order in which you tighten the bolts. You can't just tighten them willy nilly one after the other. It's like a cross sectioning pattern you have to follow
I did follow the torque order, however I didn't have a torque wrench at the time. Is it possible to cause damage to the gasket by over torqueing the bolts?
Yes there is, especially if you're reusing the same bolts. BMW rule of thumb, ALWAYS use new bolts.
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      12-26-2020, 10:49 PM   #6
ultimta
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Quote:
Originally Posted by thomas1097 View Post
Yes there is, especially if you're reusing the same bolts. BMW rule of thumb, ALWAYS use new bolts.
Would I be able to tell if the gasket is damaged by visually inspecting it?
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      12-26-2020, 11:07 PM   #7
thomas1097
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Quote:
Originally Posted by ultimta View Post
Quote:
Originally Posted by thomas1097 View Post
Yes there is, especially if you're reusing the same bolts. BMW rule of thumb, ALWAYS use new bolts.
Would I be able to tell if the gasket is damaged by visually inspecting it?
Quote:
Originally Posted by ultimta View Post
Quote:
Originally Posted by thomas1097 View Post
Yes there is, especially if you're reusing the same bolts. BMW rule of thumb, ALWAYS use new bolts.
Would I be able to tell if the gasket is damaged by visually inspecting it?
I don't think so. You would have to remove the pan to visually inspect. I would do it anyway and replace those bolts.
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      12-26-2020, 11:22 PM   #8
ultimta
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Quote:
Originally Posted by thomas1097 View Post
I don't think so. You would have to remove the pan to visually inspect. I would do it anyway and replace those bolts.
Iím going to add more fluid for the time being and then this weekend I will drop the pan and replace the bolts. Thanks for the help
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