[MikesX35i]

So ever since two weeks ago when Oregon had the 14 degree weather, my car has been acting different. When I went to go start it a couple days after that week (since I wasn’t driving anywhere) I got a message on prime saying that the coolant was low. Filled it up and everything was good until today when I realized that coolant was leaking from the from of the car. To me it looks like the hose gave out at some point and has been slowly leaking coolant. If someone can help me with identifying what part/parts I need to replace, that would be appreciated. The photos attached are where I see the leak most prominently.

[Hellshalfacre]

Hey Mike, I just had the same issue on my '17. Mine ended up being a leaking radiator. Best way to determine what is leaking is to pressure test. If it is just the lower transcooler line, the oring is very simple to replace. All new orings came in my radiator kit, but they are available at the parts desk as well. I was pretty surprised to see a failed radiator with only 76k on the car, but it's a very straightforward swap if that ends up being your issue. All parts stores will rent you the coolant pressure tester for free.

[MikesX35i]

Providing more pictures below, trying to figure out what hose this is..

[Hellshalfacre]

That hose is the lower transcooler hose. It goes from the lower portion of the radiator to the upper transcooler connection. It may be leaking, or the radiator could be leaking onto the hose. Do this:

Clean it up as best you can, blow off any fluid with compressed air if you have it. Fold a paper towel down to about an inch. Wrap it tightly around the hose connection. Start the engine. Run for a minute and pull off the towel. If the inside of the towel is wet and the outside is dry,, the hose connection is leaking. if the reverse is the case, then the leak is coming from either the cooler or the radiator. Run your finger under the upper tanscooler hose connection to make sure it's not coming from there and dripping onto the lower connection. Or...rent a pressure tester and you'll be able to see in 2 seconds where the leak is coming from.

[chris55552]

I just went through this ordeal 2 weeks ago, and I think your pics are identical to mine. The good news is its an easy DIY fix, I ended up getting a new radiator for 175 nissens version, and bam everything is fixed. Radiator replacement is pretty easy on the F25. Im mechanically challenged yet still able to pull it off.

[MikesX35i]

Hellshalfacre chris55552

I have an update for both of you and I need to know what you guys think.

I ran the car this morning after getting the ramps and waited for the car to warm up and the thermostat to open, prior to doing this I thought that the leak was from the pipe in the pictures posted previously. As it turns out, I checked for leaks after letting it warm up and found the culprit. I need to know what to do next.

[chris55552]

Replace the radiator, without a doubt. Yours looks exactly like mine did when I removed it and its also leaking from the exact same area. So sorry im late responding, you have probably already resolved it but if not shoot me any questions. But the best course of action is going to be replacing the radiator, I went with nissens brand which is a good quality brand also recommended by other bmw owners and it was only about 175 I think. Install is relatively easy even for an idiot like me in a mechanical sense. Remember to do the coolant bleed procedure while topping it off with new replacement coolant, it sure makes it easier.

[Hellshalfacre]

Sorry Mike, was offline for a bit. 100% with Chris on this. Check out the radiator replacement thread for a few gotchas, but it's a very straight forward and intuitive replacement. I also went with Nissens and it's exactly the same as the unit that came out of the car. Comes with all the orings as well. Good luck and reach out if you have any questions about the process.