As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING APU RUN, AIRPLANE FILLED WITH SMOKE, THE SMOKE HAD A BURNING RUBBER SMELL. T/S TO CABIN ACM TURBINE BEING SEIZED. REMOVED FWD ACM IAW MM 21-51-00 8/22 REMOVED COALESCER SOCK FROM WATER SEPARATOR. ATTEMPTED TO CLEAN COALESCER SOCK SEVERAL TIMES BUT UNABLE TO REMOVED THE SMELL OF OIL. 8/22 OK TO INSTALL NEW COALESCER SOCK. INSTALLED NEW COALESCER SOCK IAW MM 12-10-01. 8/22 INSTALLED ACM IAW MM 21-51-00. OPS CHECK LEAK CHECK GOOD 8/23.