My Rad makes a tapping noise?

[wazzag]

Just installed a new double rad in the lounge and its making a tapping sounds every now and then. It sounds like a finger nail tapping on the rad!?
Any ideas anyone?

 

[superdupergasman]

Pipe pushed up agains a joist or floorboard. then expanding as hot water flows through it.

 

[wiggikins]

Solder in pipework?? (possibly excess from your leaky elbow i am assuming).

 

[Aquaheat]

did you fit the plastic guides in the brackets!!??