That small quick coupler on front of your machine is a case drain , a case drain rock filter assembly is already installed on that hose , trace the hose from on side the battery and you will find it , a 2" round aluminum tube ----------- since it worked on another machine then probally the hoses are backwards or the aux hydraulics are not working at all , with nothing hooked to the machine when you engage the aux you should hear hydraulic oil by bypassing ------------- in a perfect world a plate compactor should be run on a curcuit that is unrestricted to tank on the return side , what happens is the self centering spool valve of the Bobcat traps pressure in the lines when it is centered , the motor seals of the plate are very sensitive to pressure , so if you run a case drain line from the motor back to the machine it could help prevent damage to the seal -------------- I see alot of plates around here , they drive 30 and 40 ft pilings in the ground with them