What was found
LEFT ENGINE BLEED OVERHEAT EICAS MESSAGE PERFORMED QRH PROCEDURE, LIGHT EXTINGUISHED. AIRCRAFT BACK TO BLOCK AND GROUNDED BY MAINTENANCE. MAINTENANCE AS PER FIM 36-10 F/T 867. FOUND PRSOV FAULTY, REMOVED AND REPLACED LEFT ENG. PRSOV ASSY. IAW AMM 36-11-09, NO CLEAR LEAKS NOTED, PART EFFECTIVITY VERIFIED. A/C RETURNED TO SERVICE. AICRAFT DEPARTED AND HAD L ENG BLEED LIGHT ILLUMINATED ASSOCIATED WITH L PACK OFF.CREW ELECTED TO RETURN TO MIA AND LANDED WITH OUT FURTHER INCIDENT. AIRCRAFT WAS GROUNDED BY MAINTENANCE. MAINTENANCE REMOVED AND REPLACED PRESSURE REGULATIONG VALVE CONTROLLER IAW AMM 36-11-18 PERFORMED ENGINE RUN UP. IAW AMM 70-00-00 OPS CHECK NORMAL. PART EFFECTIVITY VERIFIED A/C REMAINS NO ETOPS. AIRCRAFT RETURNED TO SERVICE.