As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX- ON FLIGHT 2501 (PDX-BUR) WHEN THE RIGHT AIR CONDITIONING PACK WAS SELECTED THE CABIN FILLED WITH SMOKE. CABIN WOULD NOT COOL IN AUTO OR MANUAL. MAINTENANCE FOUND RIGHT AIR CYCLE MACHINE VIBRATES BADLY AND EMITS A SQUEALING SOUND. PLACED ON MEL 21-51-1B. AIRCRAFT RETURNED TO SERVICE.