AN ACR B727 FLC HAD 2 #1 STRUT OVERHEAT WARNINGS ILLUMINATE RESULTING IN 2 EMER PROCS AND RETURNS TO TPA. THE MAINT TECHNICIANS; APPARENTLY; ASSUMED THAT THE FIRST PROB WAS A TEMP REGULATOR UPSTREAM OF THE #1 AIR BLEED VALVE. HOWEVER; THE OVERHEAT WARNING AGAIN ILLUMINATED BECAUSE THERE WAS; INSTEAD; A CRACK IN THE DUCT BTWN THE ENG BLEED OUTLET AND THE VALVE.

Narrative

AT 1500 FT AFL AT MAX PWR; #1 STRUT OVERHEAT LIGHT ILLUMINATED. OM CHKLIST ACCOMPLISHED AND APPROX 2 MINS AFTER #1 BLEED VALVE CLOSED; LIGHT WENT OUT. DUMPED FUEL AND RETURNED TO TPA. AT TPA; MAINT ADVISED THEY WOULD BE PLACARDING THE #1 BLEED AND RE-DISPATCHING US TO DFW. I ADVISED THAT WE COULD NOT USE ALTERNATE BLEED SOURCE FOR L PACK IN THIS CONFIGN IN ACCORDANCE WITH THE OM STRUT OVERHEAT PROC AND WOULD BE IN SINGLE-PACK OPS; THEY REPEATEDLY TRIED TO CONVINCE US THIS WAS UNNECESSARY. CONSULTATION WITH TULSA TECHNICIAN PRODUCED NO BETTER RESULT. CAPT REQUESTED AN INSPECTION OF STRUT AREA FOR POSSIBLE DAMAGE; NONE FOUND. MAINT THEN PROPOSED PLACARDING L PACK (21-1) L DUCT ISOLATION VALVE (36-1C) AND #1 13TH STAGE BLEED AIR VALVE AND SHUTOFF (36-8). THE INTENT WAS TO LEAVE BOTH #1 BLEED VALVE AND L DUCT ISOLATION VALVE CLOSED FOR THE REST OF THE FLT. SINCE #1 STRUT OVERHEAT HAD BEEN REMEDIED BY CLOSING #1 BLEED VALVE; THOUGHT WAS THAT ALLEGED LEAK WAS INBOARD OF THE BLEED VALVE AND ISOLATING THIS SECTION OF DUCT WOULD PREVENT ANOTHER OVERHEAT. THOUGH CONCERNED THAT WE WERE STRETCHING THE INTENT OF MEL ITEMS SINCE NO CAUSE OF THE OVERHEAT HAD ACTUALLY BEEN DETERMINED; MAINT WAS VERY INSISTENT THAT THIS WAS WELL BEYOND WHAT WAS ACTUALLY NEEDED. THEY STILL ADVISED THAT WE COULD GO WITH JUST #1 BLEED PLACARDED AND USE #2 AS A BLEED SOURCE FOR L PACK AFTER TKOF. AFTER COORD WITH BOTH DISPATCH AND TULSA; CAPT ACCEPTED A RELEASE WITH ITEMS 21-1; 36-1C; AND 36-8 PLACARDED FOR A SINGLE-PACK RETURN TO DFW AT FL240. DEPARTED AND AT 7000 FT AFL; AT CLB PWR; #1 STRUT OVERHEAT ILLUMINATED AGAIN. WAS TO REDUCE #1 THROTTLE. AT APPROX 1.7 EPR LIGHT WENT OUT. DUMPED FUEL AND RETURNED TO TPA. ACFT TAKEN OTS AND MAINT FOUND CRACK IN A BLEED LINE BTWN ENG AND #1 BLEED VALVE. IN HINDSIGHT; I FEEL WHEN OVERHEAT LIGHT WENT OUT AFTER WE CLOSED #1 BLEED DURING THE FIRST OCCURRENCE; IT WAS ACTUALLY EXTINGUISHED AS RESULT OF PWR REDUCTION IN PREPARATION FOR RETURN TO TPA AND NOT BY CLOSING OF BLEED VALVE. THIS CONFUSION LED US DOWN A CHAIN OF REASONING THAT LED US TO ACCEPT ACFT FOR SECOND FLT WHERE OVERHEAT RECURRED. IN THE FUTURE; I WILL BE MORE FORCEFUL IN EXPRESSING MY DESIRE THAT ACTUAL CAUSE OF SUCH A WARNING BE CONFIRMED BY MAINT BEFORE LOOKING TO MEL FOR LEGALITY OF DISPATCHING WITH A PROB. WHILE I FEEL WE WERE LED DOWN THE PATH BY MAINT ON THIS ONE; WE MUST SAY TIME OUT WHEN THEIR ANSWER DOESN'T FIT WITH OUR UNDERSTANDING OF THE SYS OR VIOLATES OUR COMFORT ZONE.