Check ET for leak carefully. Clean up residue, top off (to between min and max) get it up to op temp and see, for sure, where it's leaking from.
ET cracks in corners or on horizontal seam.
ET cap can leak, and bleeder screw can get cracked.
The rest of what you said sounds right. GL!
Upcoming NYC dates: Jan 8 and 27. See Facebook for other shows and PM me if you can make one...love to see you there!
Mangofy your E46!