nubiranutter

hi guys got a problem with the low fiel level light it does not come on when the petrol level is low has anyone else had this problem. also knocking cpming from front end when I go over a bump in road i replace both front wishbones last year but still got problem any ideas? the car is a 98 nubria 2.0 cdx auto estate with 43ooo miles on her regards nubiranutter