A quick fix I applied to my engine cover bolt caps. They rattle quite badly in the cover, and it seems that the problem is that the engine cover itself wears, allowing them to much movement (I already tried replacing the caps, as they are cheap). So I applied a quick fix to the back of the caps, using 3 pieces of wiring loom tape and trimming round the edges. No more rattles. . We will see if the adhesive holds up.

Great tip, 

 

The badge and shiny plastic surround rattled like a bugger on mine so i removed them, cleaned the plastics then put some silicone sealant beneath them, the silence is wonderful now