L322 Front shockers

Hi all 2003 vogue td6 with 185,000 miles on the clock .
Air suspension works well but over bad roads I'm getting bumping noises from the front .
I'm beginning to think it may be the shock absorbers . The black plastic covers over the top of them in the engine bay won't stay on . I fit it ,2 miles down the road and it's off. Is there some way I can test the shock absorber ? Many thanks

Sounds more like a bush or ball joint to me.

There must be some kind of bearing in the top of the strut because it turns with the wheel, but if it was bad i would expect notchy steering