hi my car would not go over 50000 rpm but seems to drive ok, so had the fault code red and came back with knock sensor. he said ihad run it a bit low on oil and that would nacker the sensor, so just to replace it and all will be well. but this morning i started car and it waz realy noise like a fanbelt noise but with a more of a rattle. seemd like bull bearings but mabey not. any way the noise goes when warmed up and will not hapen till next day. this noise started about a month ago from just a fan bell sqeek , just faught that a knock senser might be pic ing up that noise ,