If fluid level in the pump is not dropping, then you have a leaking check valve in the pump. Leaking cylinder pistons are rare. Also double check to make sure the manual valve is seated tightly in the pump (assuming you have a manual valve - some pumps have them, some do not).
As far as any bypass, the only one would be the manual release valve. A complete set of orings and check valves shouldn't run more than $30 or so.