What was found
UPON ROTATION, NOTICED UNUSUAL SMELL, AS WE CLIMBED THROUGH 4000 FEET. SMELL RESEMBLED BURNING AND BECAME STRONGER. ON DESCENT, SMELL BECAME INTERMITTENT, MOST NOTABLE IN MID / AFT CABIN. ONE FLIGHT ATTENDANT COMPLAINED OF SLIGHT STINGING TONOSE AND MOUTH. FOUND HYDRAULIC LINE TO BRAKE BOOSTER VALVE CRACKED. REPLACED SAME