@haseeb:
Nissan has a favorite way of burping its cooling systems, with some variations from model to model. It's effective if you have the patience to use the method, and not stop until a system has "bubbled" out
http://findarticles.com/p/articles/mi_qa3828/is_199808/ai_n8819552/pg_4
search google for more output 
by the way dont worry if you're buying petrol version.
just enjoy it for 8years, and then give it to your family
