What was found
EN ROUTE IAH-CUN, LOST RIGHT HYDRAULIC PRESSURE IN FLIGHT. QRH FOLLOWED, NO EMERGENCY DECLARED. REMOVED AND REPLACED O-RINGS IN THE TUBES OF THE SPOILER BYPASS VALVE IAW MM 29-10-26 AND SERVICED HYDRAULIC SYSTEM, WHICH WAS LOW, TO NORMAL LEVELS. AIRCRAFT REPOSITION CUN-IAH AS A MAINTENANCE PRECAUTIONARY. CHECK AND REPLACE RETURN AND CASE DRAIN FILTERS IN RIGHT HYDRAULIC SYSTEM. REMOVED AND REPLACED RETURN AND CASE DRAIN FILTERS IN RIGHT HYDRAULIC SYSTEM. NO DISCREPANCIES NOTED.