There could be a variety of reasons for the knocking sound. One of the reasons could be one of your engine sensors which needed to be replaced by a mechanic.
If the sound occurs only when the fan is moving it could be the bearings within the fan. If the sound occurs even when the fan is not running then it could be a problem within the engine such as vales.
There could be a variety of reasons why there is a knocking sound of the pick up. It could be a ball bearing that is lose or it could be a braking issue which needs to be check out by a mechanic.
