Those "bleeders" are actually "system pressure release valves" designed to be used for releasing pressure in the lines to a cylinder before disconnecting them so as to avoid getting sprayed with high pressure oil.
Usually in the implement system the method of removing any trapped air would be to work the cylinder back and forth through its full stroke with the engine at low idle. That should get all the trapped air back to the tank and a simple top-up of oil completes the process.
You can bleed the Implement Pilot system. Here is the procedure.
MAIN CONTROL VALVES
Valves marked 1-7. Bleed valves for the release of air from the pilot system oil.
1. Install the swing lock pin and lower the boom assembly to the ground.
2. Turn the plunger on the track brake valve all the way in.
3. Start the engine and set the governor control to high idle.
4. Move the safety lever to the OPERATE position.
5. Move the control lever for swing movement to the bumper spring for swing RIGHT position and hold it there.
6. Open bleed valve (7) one-half turn and make adjustment as needed to remove air from the housing.
7. Tighten bleed valve (7) when there is no more air in the oil flow from the bleed valve opening.
8. Move the control lever to NEUTRAL.
9. Do Steps 5, 6, 7 and 8 for swing LEFT using the bleed valve on the inboard end of the swing valve. [Opposite bleed valve (7)].
10. Do steps 5, 6, 7 and 8 for bucket OPEN. Use the control lever for bucket movement and bleed valve (2).
11. Do steps 5, 6, 7 and 8 for bucket CLOSED. Use the control lever for bucket movement and the bleed valve on the inboard end of the bucket valve. [Opposite bleed valve (2)].
12. Do Steps 5, 6, 7 and 8 for boom LOWER. Use the control lever for boom movement and bleed valve (1).
13. Do Steps 5, 6, 7 and 8 for stick OUT. Use the control lever for stick movement and bleed valves (4) and (5).
14. Do Steps 5, 6, 7 and 8 for boom RAISE. Use the control lever for boom movement and the bleed valves on the inboard end of the boom valve and the boom crossover valve. [Opposite bleed valves (1) and (4)].
15. Do Steps 5, 6, 7 and 8 for stick IN. Use the control lever for stick movement and the bleed valve on the inboard end of the stick valve. [Opposite bleed valve (5)].
16. Push down on the right pedal and hold. Do Step 6 and 7. Use bleed valves (3) and (6).
17. Push down on the left pedal and hold. Do Steps 6 and 7. Use bleed valves on the opposite end of the right and left track valves. [Opposite bleed valves (3) and (6)].
18. Turn the plunger on the track brake valve all the way out.