What was found
AFTER TAKEOFF, DURING CLIMBOUT, REPORTED AFT EQUIPMENT BAY OVERHEAT LIGHT ON MASTER CAUTION WARNING PANEL ILLUMINATED. RETURNED TO PLACE OF ORIGIN. AFTER TROUBLESHOOTING FOUND DETERIORATED BLEED VALVE SEAL ON RT ENGINE BLEED AIR SHUTOFF VALVE IN AFT EQUIPMENT BAY. REPLACED DEFECTIVE SEAL WITH NEW SEAL. RAN BOTH ENGINES AT POWER AND PERFORMED OPERATIONAL AND LEAK CHECK. NO DISCREPANCIES NOTED. SUSPECT CAUSE OF DEFECTS SHRINKAGE OF SEAL OVER PERIOD OF TIME. RECOMMEND PERIODIC BLEED AIR LEAK CHECKS AND TORQUE CHECKS OF BLEED AIR MARMON CLAMPS.