Find out where the motor is coming into contact with whatever it is it's coming into contact with - and put a piece of foam in the gap to dampen the movement.
It makes no sense to me that the banging is due to the fridge not getting enough coolant - no sense at all.
They mount fridge motors on anti-vibration supports - fridge motors wobble - if an AV mount perishes then this may well cause the banging - but I just guess - it needs looking at.
Peccavi
February 2013