BMW X3 Coolant Expansion Tank Leak and Replacement Fix E83

coolant expansion tank

If your BMW X3 low coolant light comes on, it’s normal to have to top off the tank once or twice a year. But if you top off your tank and the low coolant light comes on again within a few days or a week, then you probably have coolant leaking from the system somewhere. First, check the back of the oil fill cap and make sure you see only brown oil as expected. If it’s foamy or creamy texture, you might have a head gasket leak. Most likely you don’t have a head gasket leak and it’s a coolant hose or coolant expansion tank leak. In the video below I explain how to diagnose a BMW X3 coolant expansion tank leak and how to replace the tank.

As you can see in my video, I had a small leak that didn’t even puddle water in the garage, at first. But the leak quickly became worse and I found myself topping off the coolant tank every day or two toward the end before repairing it.

low coolant symbol

Low Coolant Level Warning Light

First, order the replacement expansion tank and coolant you’ll need. I purchased my parts on Amazon here:

BMW Expansion tank:
BMW compatible coolant: (I just used the cheaper alternative instead of the BMW blue coolant)

When you do this service, you may want to replace the upper radiator hose and radiator cap like I did as a preventative maintenance step:

BMW upper radiator hose:
New Radiator Cap:

Next, it’s easiest to just watch the video a few times and see what the replacement procedure will be like. It took me 2 to 3 hours to do and that was shooting video as I went. Take your time to make sure you do the job right if you don’t want any leaks. Also see more tips listed below.

This repair was my first time using the BMW quick release coolant hoses. They worked great and were easy to use, just pop the clip up and then wiggle the hose off. To reattach, slide the clip back down and then slide the hose back on until it clicks. Before reattaching, I used some brake clean on a microfiber towel and cleaned the O ring that’s inside each hose. If your coolant was recently changed and is clean, this step may not be required, but I still recommend it to avoid leaks.

I also recommend only genuine Bosch or BMW parts for the BMW X3 coolant tank replacement procedure. Again, you don’t want any leaks or for a part to fail right away. For this kind of repair it’s worth it to buy the genuine replacement parts. As far as the coolant level sensor and temperature sensor, I reused mine and left them where they were when I had the tank out. As a note, when the tank was out I did have to clean some plastic pieces out of the sensors that broke off from the old coolant tank.

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