[prshuk]

I recently discovered a coolant leak in my 2010 BMW 328i (E90). After driving yesterday, I noticed a significant leak from the underside of the car. I checked the return line hose from the coolant reservoir and the hose running from the thermostat to the cylinder without finding any leaks. However, I observed some leakage around the right side of the radiator, as illustrated in the attached photos.

Does this suggest a need to replace the radiator, or could there be another issue at play? The photos attempt to show the leak area, though it's tough to clearly depict the fluid escape.

I would appreciate any insights or advice on whether my diagnosis is accurate and what my options for repair might be. Thank you in advance for your help!

[mainbearing]

In the pictures it looks like the leak is at the seam of the core and the plastic tank? The hoses look dry.

You can take a closer look around there. If it is leaking from the seam then yes a new radiator. It may be a good time to change out the hoses too.

TX is not a CARB state, so that radiator likely is not covered under the ozone reduction emissions warranty.

[lookalikehuuh]

I have had good luck with starting the coolant purge process (turning the ignition switch to the "on" position, without starting the engine, set heater to highest temp and fan to lowest speed. Then hold the accelerator pedal to the floor for 10-15 seconds. It will start the water pump to move coolant throughout the system and can help you locate exactly where the coolant leak is coming from. To stop the process just turn the car off by pushing the ignition button again.

Its fairly common to have the radiators fail where the aluminum core meets the plastic endcaps. Lots of us have struggled with constant radiator failures to the point where I think the only even remotely semi reliable radiator for the e90 chassis are the Genuine BMW radiators. I personally have gone thru Mahle/BEHR units about once a year or two on my cars. I basically have radiator swaps down to a science and can do it in like an hour give or take 10 mins.

[watchout-everyone]

Upper radiator hose ($25)

https://www.fcpeuro.com/products/bmw...er-17127531579

If I were you, I would honestly clean it (water + cloth) then drive one more time to check if there are any other hoses that's also damaged. I remember replacing a damaged hose just to find out another one nearby was also leaking (so essentially it became two separate order/jobs).

Good luck!

[prshuk]

Originally Posted by mainbearing

In the pictures it looks like the leak is at the seam of the core and the plastic tank? The hoses look dry.

You can take a closer look around there. If it is leaking from the seam then yes a new radiator. It may be a good time to change out the hoses too.

TX is not a CARB state, so that radiator likely is not covered under the ozone reduction emissions warranty.

Yes, I've inspected it multiple times, and it does appear the leak is coming from the seam between the core and the plastic tank. Based on your advice, I've ordered a replacement radiator and new hoses to ensure a thorough fix. Thanks for the tip on checking the emissions warranty in Texas.

[prshuk]

Originally Posted by lookalikehuuh

I have had good luck with starting the coolant purge process (turning the ignition switch to the "on" position, without starting the engine, set heater to highest temp and fan to lowest speed. Then hold the accelerator pedal to the floor for 10-15 seconds. It will start the water pump to move coolant throughout the system and can help you locate exactly where the coolant leak is coming from. To stop the process just turn the car off by pushing the ignition button again.

Its fairly common to have the radiators fail where the aluminum core meets the plastic endcaps. Lots of us have struggled with constant radiator failures to the point where I think the only even remotely semi reliable radiator for the e90 chassis are the Genuine BMW radiators. I personally have gone thru Mahle/BEHR units about once a year or two on my cars. I basically have radiator swaps down to a science and can do it in like an hour give or take 10 mins.

Thanks for the detailed walkthrough on the coolant purge process—I tried it and confirmed the leak seems to be coming from the seams. I appreciate the heads-up about the common failure at the core and endcaps junction on the E90s. Based on your experiences with different brands, I’ve opted for a Genuine BMW radiator from FCPEuro to hopefully avoid frequent replacements. You seem to have mastered the swap process! If I encounter any issues during installation, I may reach out for some of your expert tips.

[prshuk]

Originally Posted by watchout-everyone

Upper radiator hose ($25)

https://www.fcpeuro.com/products/bmw...er-17127531579

If I were you, I would honestly clean it (water + cloth) then drive one more time to check if there are any other hoses that's also damaged. I remember replacing a damaged hose just to find out another one nearby was also leaking (so essentially it became two separate order/jobs).

Good luck!

Thanks for the advice and the link to the upper radiator hose; I've ordered it. I also took it for a drive to double-check for any additional leaks and didn't notice any. It was a good call to inspect nearby hoses as well—better to catch everything in one go. I appreciate your help!

[lookalikehuuh]

Originally Posted by prshuk

Thanks for the detailed walkthrough on the coolant purge process—I tried it and confirmed the leak seems to be coming from the seams. I appreciate the heads-up about the common failure at the core and endcaps junction on the E90s. Based on your experiences with different brands, I’ve opted for a Genuine BMW radiator from FCPEuro to hopefully avoid frequent replacements. You seem to have mastered the swap process! If I encounter any issues during installation, I may reach out for some of your expert tips.

Yeah man for sure, I will tell you the most difficult part is going to be getting the large hose connector on the passenger side off the radiator. I find it easiest to remove the metal clip entirely, then use a long pry bar to work it off. Take your time and don't be afraid to use a bit of muscle on that connection, it's always a pain. Otherwise the rest of the process is pretty straight forward.

Take your time and watch a couple of youtube videos before you tackle it and you will be solid.

I would also recommend you consider replacing the upper radiator hose (its likely to break the nipple off) and the expansion tank hose (the one that goes on top of the radiator and is half plastic line/half hose).