A B747-400 PILOT IS CONCERNED WITH THE DEFERRAL OF A #4 HYD SYS TEMP INDICATION AND BELIEVES THE DEFERRAL DOES NOT CONTAIN ENOUGH INFO FOR FLT CREW.

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DEFERRED ITEM DOES NOT CONTAIN ENOUGH FLT CREW INFO. WITH THIS CONDITION OF #4 HYD TEMP FLUCTUATING HIGH FROM 55 DEGS TO 115 DEGS. DEFERRED ITEM MAKES NO MENTION THAT THE 'SYS FAULT' LIGHT REMAINS ON CONTINUOUSLY; ONLY THAT THE LIGHT OPERATE NORMALLY. DEFERRED ITEM MAKES NO MENTION THAT THE #4 HYD SYS NOW HAS NO MEANS TO MONITOR TEMP SHOULD A SUBSEQUENT ACTUAL OVERHEAT OCCUR. I FIND THIS DISTURBING TO FLY A 12 HR LEG WITH A #4 HYD TEMP PEGGED OUT; AN EMBER 'HYD OVERHEAT SYS 4' EICAS MESSAGE; AND 'SYS FAULT/OVERHEAD LIGHT' STARING ME IN THE FACE. ALL THAT IS MENTIONED IN LOG HISTORY IS THAT HYD TEMP WAS CHKED OK ON GND. HOW WAS THE CHK PERFORMED? AFTER CONSULTING MAINT; WE COLLECTIVELY DETERMINED THAT THE #4 TEMP IS A SINGLE SOURCE PROBE THAT TRIGGERS ALL 3 LIGHTS (EICAS HYD OVERHEAT SYS 4; SYS FAULT-OVERHEAD; AND AMBER DIGITAL TEMP READOUT ON HYD SYNOPTIC). ALSO; HYD QUANTITY INDICATION MUST BE AVAILABLE FOR THIS DEFERRED ITEM. SO; BASICALLY; WE FLY ALONG FOR 12 HRS WITH A SINGLE SOURCE TEMP PROBE INOP; BUT SHOWING PEGGED; OUT WITH NO SECONDARY WAY TO MONITOR HYD TEMP. SO THE DEFERRED ITEM ALLOWS THE #4 SYS TO BURN ITSELF OFF THE ACCESSORY CASE OF THE #4 ENG AND YOUR BACKUP FOR MONITORING SYS TEMP IS WHEN THE FLUID DRAINS FROM THE SYS AT POINT OF FAILURE. THE DEFERRED ITEM NEEDS TO BE REWRITTEN AND FIXED AT FIRST MAINT OPPORTUNITY AVAILABLE. I WILL NOT ACCEPT THIS CONDITION FOR THIS LONG OF FLT NEXT TIME. MY FO STATED HE HAD THIS ACFT ON A FLT IN JUNE. THIS NEEDS TO BE REPAIRED ASAP. THERE APPEARS TO BE NO TEMP MONITORING REDUNDANCY UNTIL POINT OF FAILURE OF THE #4 SYS. MORE INFO MUST BE INCLUDED FOR THE FLT CREW'S NOTES FOR FUTURE DEFERRED ITEM AND SHORTER FLT TIME LIMIT.