As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WITH POWER APPLIED THERE WAS A SMELL LIKE BURNING RUBBER. SMELL DISSIPATED WITH POWER BACK, NO INDICATIONS. RAN BOTH ENGS TO T/O POWER WITH PACKS ON, ANTI-ICE ON. CHECKED AIR MIX DISTRIBUTION PLENUM IN FWD B/B, NO CRACKS. REPLACED BOTH WATER SEPARATOR BAGS, LEAK CHECKS OK.