What was found
DURING TAKEOFF, CREW NOTICED A LOUD SQUEAL COMING FROM THE AREA NEAR THE EMERGENCY OVER WING EXIT. TECHS SET UP FOR ENG RUN. AFTER ENGINES ARE STARTED, WE PRESSUREIZED THE CABIN TO DELTA 0.7 AND HEARD THE SQUEAL FROM EMERGENCY EXIT. REMOVED EMERGENCY EXIT AND COMPLETED GVI OF THE EXIT. FOUND LOTS OF DIRT ON VENT FLAP. CLEANED AND REINSTALLED EMER EXIT. THREE TECHS STARTED ENG AND PRESSURED TO DELTA 1.0 WITH NO SQUEAL NOISE. NO FURTHER DISCREPANCIES NOTED. REF: AMM 52-20-20