What was found
REAR EQUIPMENT BAY OVERHEAT "RED" LIGHT ILLUMINATED AT 8000 FT MSL, DURING CLIMB. APU BLEED SWITCH OFF & APU STOPPED, THROTTLES REDUCED, "RED" LIGHT EXTINGUISHED & REAR EQUIPMENT BAY OVERHEAT CHECKLIST COMPLETED JUST AFTER POWER REDUCTION. MASTER WARNING SYSTEM ILLUMINATED WITH NO MASTER WARNING PANEL LIGHTS INITALLY, THEN THE MASTER WARNING SYSTEM ILLUMINATED WITH AN ASSOCIATED REAR EQUIPMENT BAY OVERHEAT LIGHT A FEW SECONDS LATER. FOUND BLEED AIR LEAK AT NR 1 ENGINE MAIN AIR VALVE. R & R NR 1 ENGINE MAIN AIR VALVE IAW MM 21-10-25. OPS AND LEAK CHECKED GOOD.