Random temp jumping is a sign of poor water flow in the tubes by the way i would make sure they are not twisted.
the answer to your question really depends on how your computer is set up.
Ideally you want to be forcing more air into a computer case than out of it to help reduce dust buildup and improve cooling. For example my case has two front 140mm fans as intakes, my radiator set as an intake on the bottom (dual 140mm) and im using a rear 120mm right next to the radiator (my case is a corsair 600c its an inverted atx case so everything is upside down) to pull hot cpu air out and my power supply fan to also pull some air out.
Thus the airflow path is front and bottom to back and top. you want a linear path like this for your airflow...