What was found
WHEN ENTERING THE RWY FOR T/O, L HYD QTY EICAS CAUTION MESSAGE DISPLAYED AND RSVR ON THE OVERHEAD PANEL ILLUMINATED FOR THE L HYDRAULIC SYSTEM. THE EICAS STATUS PAGE DISPLAYED A MAGENTA RF BY THE L HYD QUANTITY AMOUNT. THE THRUST LEVERS WERE NEVER ADVANCED FOR T/O. AFTER CLEARING THE RW, ALL CAUTIONS AND MESSAGES DISAPPEARED. ALL INDICATIONS SHOWED TO BE NORMAL. REMOVED THE HYDRAULIC FLUID QUANTITY MONITOR UNIT AND INSTALLED A SERVICEABLE HYDRAULIC FLUID QUANTITY UNIT REFERENCING THE AMM 29-33-51-4. OPERATIONAL CHECKS GOOD FOR FUNCTION AND SECURITY. OKAY TO CONTINUE.