Personally I would fill it up with water and pressure test it. The coolant pipe is probably right but what if there are other leaks? I bought a harbor freight pressure test kit for and it worked fine to point out the leak in my e46 radiator. I went that route since I was worried I would replace the radiator or expansion and then find another leak after I put it all back together. If you do not want to buy one most shops will do the test for 50.00 or so.

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2004 E60 545i Sport 6MT. Black/Black Build Date 6-2004 102k miles