On these M57 diesel engines internal coolant leaks are like winning a lottery. The only thing that could cause coolant leak into chambers is EGR cooler which grounch does not have in his EU3 variant.

I would probably renew the CCV valve housing and vortex separator anyways. And in the same time remove air pipe between MAF and turbo and check the play on turbo axle and see the condition of the compressor wheel. Small under 1 mm radial play is normal, no axial play in normal condition turbo.

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E39 530dA -02 M-Sport Messing metallic
E53 X5 3.0dA -06 Sport Stratus grey
E70 X5 40d -12 M-Sport Space grey