Polar 115XT Air bubbles in hydraulic oil

I have recently purchased a 2004 Polar 115 XT which was in working condition.
I have changed the hydraulic oil an the machine (without bleeding the system) and the machine is working. However before replacing the oil cover I noticed how the oil was changing its color to white because of all the air bubbles. As soon as I put my foot on the foot pedal it got even worse.

Is this because I have not bled the hydraulic system ? How do I bleed the system on this more recent model machine ?

I have also removed the hydraulic block and changed all the o-rings but this has not made any difference.

Has anyone got some advice ?

 

Change the seals on the pump that is usually where air gets in. This model shouldn't need bleeding but there is usually a bleed port on the clutch ram at the back just above where oil pipe enters the ram