air lock hyra. pump possible ?

[TravisTractor]

my father changed filter and cleaned screen in hydra. res. now the pump won't pick up oil is it possible for this to air lock?, any ideas welcome. 5400 jd. bosh pump,

 

[Glen Watkins]

When I did a hyd. oil change my manual said Fill the filter 1/3 to 1/2 full with oil. Try it!

 

[TravisTractor]

thanks,