Tranmission Cooler Replacement Question
 

this question isn't for an X5, but rather e60LCI. The e60 forum isn't as active as this one. which is why i figured i post my question here.

i have a 2009 528i with a hole in the transmission cooler attached to this radiator. i'm planning on changing it this weekend. my question is do i need to add transmission fluid to the transmission after i replaced the cooler?

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thanks,

I would assume you're going to lose some fluid in process so I would top it off.

I agree with smokeyyank, already having a hole and removing and replacing the t-cooler will definitely put you down enough fluid to potentially cause wonkie shifting issues for sure - I would definitely make sure that is topped off.


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Where is the hole exactly?

I had a hole in the core of my trans cooler on the 3.0i where ATF was leaking into the cooling system. A routine coolant check showed mayo under the reservoir cap. I thought I blew the headgasket or cracked the head but a last ditch check on the ATF cooler via pressure test showed the leak and we started there, lucky it solved it in my case.

If there is crossing over I would change out the coolant and the ATF. Water contamination of the trans fluid has the potential to kill your tranny. Mercedes comes to mind with the W203 C and W211 E's having ATF contamination via the radiator oil cooler that has killed a lot of transmissions.

When I replaced my cooler I replaced coolant and ATF to be safe.

Oh, and IIRC the only way to know if you need to add ATF is to open the fill plug and check ATF level there at a certain temp. Anything other than that would be guessing.

Also, I think the trans coolers have o-ring seals that would be a good idea to replace at the same time.

Yep, on the X they call them "X-Rings"(2 each needed):thumbup: