What was found
AIR RETURN, NR 2 ENG OVERHEAT CAUTION LIGHT ILLUM TWICE. DECLARED EMERGENCY, LANDED W/O INCIDENT. ON DESCENT, MASTER CAUTION SYS ILLUM 4 TIMES, NO SIX PACK INDICATION. MX TESTED CAUTION SYS THRU SIMULATION OF CONDITIONS CAUSING ILLUMIN ANNUNCIATORS, ALL SYS OPERATED NORM. COULD NOT DUPLICATE. REPLACED NR 2 ENG PRSOV, LEAK CHECKED OK. PERFORMED LEAK CHECK NR 2 ENG AIR DUCTS, NO LEAKS FOUND. RAN NR 2 ENG AT T/O POWER APPROX 2 MIN & ENG OVERHEAT LIGHT ILLUM. SWITCHED OVER TO A-LOOP, FAULT REMAINED. SWITCHED TO B-LOOP, FAULT WENT AWAY. PROBLEM COULD ONLY BE DUPLICATED WITH ENGINE HOT. PLACARD NR 2 ENG A-LOOP, COMPLIED WITH SPECIAL PROCEDURES. PERFORMED OVERWEIGHT LANDING INSPECTION, NO DEFECTS FOUND.