BA3201 ACFT AFTER TKOF AND RAISING LNDG GEAR; IT WOULDN'T COME UP DUE TO FLUCTUATING HYD PRESSURE. FLC SUSPECTED AIR IN HYD LINE SINCE IT WAS THE FIRST FLT AFTER AN ENG CHANGE. FLC BEGAN TO RETURNED TO LAND AT DEP ARPT; WHEN GEAR SELECTED DOWN THE HYD PUMPS CAME BACK ON LINE NORMALLY. FLT CONTINUED TO LAX. RPTR CAPT BELIEVES HIS COMPANY SHOULD TEST FLT AN ACFT AFTER AN ENG CHANGE AND THIS SIT WOULDN'T OCCUR.

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WE WERE THE FIRST CREW TO FLY THE ACFT AFTER THE R ENG WAS REPLACED DUE TO AN EARLIER ENG FAILURE. AFTER TKOF WE RETRACTED THE GEAR AND GOT 3 RED GEAR WARNING LIGHTS AND HYD PUMP INDICATIONS THAT WERE SPORADIC AND THEN ZERO. HYD ACCUMULATOR GAUGES READ 2000 PSI. I IMMEDIATELY RECOGNIZED THE PROB AS AIR IN THE HYD LINES; AND TOLD THE FO WE WOULD CONTINUE THE CLBOUT. WE DISCUSSED THE PROB AND OUR OPTIONS WHILE WAITING TO SEE IF THE PUMPS COULD PRIME THEMSELVES AT FULL SPD. THERE IS NO CHKLIST FOR THE GEAR NOT RETRACTING. AFTER A COUPLE OF MINS; WITH NO APPARENT CHANGE IN THE HYD PRESSURE; WE CALLED THE CTLR FOR A RETURN TO LAND AT SANTA BARBARA AND SELECTED GEAR DOWN. INITIALLY THE NOSE GEAR ONLY CAME DOWN. THEN THE PUMPS CAME BACK ON LINE; THE REMAINDER OF THE GEAR EXTENDED; AND ALL INDICATIONS WERE NORMAL. AFTER A SHORT DISCUSSION BTWN THE FO AND MYSELF; WE SELECTED GEAR UP AND PROCEEDED TO OUR ORIGINAL DEST WITH NO FURTHER DIFFICULTIES. WAS THE BEST COURSE OF ACTION TO LAND IN SBA OR LAX? I'M A BIG FAN OF HAVING MY GEAR DOWN; SO ONCE THAT HAPPENED; LNDG IN SANTA BARBARA SEEMED A NATURAL CHOICE. IN TALKING WITH MY FO INITIALLY; I HAD TOLD HIM WHAT THE PROB WAS AND HOW IT WOULD FIX ITSELF AND WHAT INDICATIONS TO EXPECT. THE HYD SYS PURGED ITSELF OF AIR AND REACTED EXACTLY AS WE EXPECTED. IF IT HAD NOT WE WOULD NOT HAVE CONTINUED TO LAX. I KNEW WHAT TO EXPECT BECAUSE I HAVE SEEN THIS SIT BEFORE. OUR COMPANY HAS NO REQUIREMENT TO PERFORM A TEST FLT IF AN ENG HAS BEEN REPLACED. IF A TEST FLT HAD BEEN PERFORMED. THIS PROB WOULD HAVE BEEN SOLVED.