Creating intersection between parts

I have an aluminum block that I am running 2 stainless steel coil tubes through.  I want to subtract the space occupied by the coil tubes from the Aluminum block.  Can anyone help?  I have used the intersect command before but I can't get it to work in this case and I am not sure why.  I tried joining the coils to the Aluminum block part which seemed to work.  However, the Aluminum block is cannot be selected as a separate body as the coils in the intersect command.

Included is the assembly that has the 3 parts.

Thanks,

Marty

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