What was found
LEFT ENGINE OIL TEMP ROSE TO 200 DEGREES THEN WENT BLANK. CAME BACK ON WITH INDICATIONS NORMAL AND OUT OF LIMITS, FLUCTUATION FOR REST OF FLIGHT. RETURN TO DEPARTURE. INDICATIONS STARTED FL180 IN THE CLIMB. DURING POSTFLT DISCOVERED EICAS DISAGREE STATUS MESSAGE DISPLAYED. INDICATING AN ABNORMALITY BETWEEN LT AND RT EICAS INFORMATION REGARDING ENGINE PARAMETER(S). SPECIFICALLY THIS FAILURE OF LT ENG OIL TEMPERATURE. PERFORMED TROUBLESHOOTING IAW FIM 79-34 FAULT TREE 802. CHECKED ASSOCIATED WIRING AND CONTINUITY OF LT ENG OIL TEMP XDCR. COULD NOT DETERMINE LT OR RT EICAS OUTPUTS. WIRING CHECKS IAW WDM 79-34-01. NEEDS OIL TEMP XDCR. R & R NR 1 ENGINE OIL TEMP BULB IAW AMM 79-34-01-4. RAN ENGINE ABOVE IDLE POWER IAW JRH. SWITCHED CHANNELS ON EICAS COMPUTERS. LEAK AND OPS CHECK GOOD IAW AMM 79-00-00-501.