What was found
AFTER TAKEOFF, DURING CLIMBOUT, PILOT REPORTED AFT EQUIPMENT BYA OVERHEAT LIGHT ON MASTER CAUTION WARNING PANEL ILLUMINATED. RETURNED TO PLACE OF ORIGIN. AFTER TROUBLESHOOTING, FOUND DETERIORATED BLEED VALVE SEAL AT RIGHT 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 DEFECT IS SHRINKAGE OF SEAL OVER PERIOD OF TIME. RECOMMEND PERIODIC BLEED AIR LEAK CHECKS AND TORQUE CHECKS OF BLEEDAIR MARMON CLAMPS.