Setting REALISTIC deadlines for corrective action implementation is part of the issue. In some cases, the delinquency in implementing corrective actions is just a sympton of a dysfunctional corporate culture, where heads of departments don't feel they are accountable to a "lowly quality" person.
All ISO Management System Standards require top management to be aware and involved with the status of corrective actions in their organizations. If they allow chronic delinquency, they are derelict and there is very little a "lowly quality" person can do, in those cases.
One more aspect to consider: are the CAR's meaningful? Remember that CAR's should be triggered with caution, as you really want to deal with systemic, relevant issues. Sometimes, the reason for CAR's to be disregarded is the fact that too many spurious/trivial/irrelevant issues are mistakenly treated via a CAR, when, in reality, they should not.