Nissan Repair: Air Pockets or ...?, engine temp, air pockets

Question
Hi, Von I seem to have a problem with my '95 Pathfinder XE-V6, recently I've changed my waterpump and all the neccessary parts.(thremostat,hoses,timing belt,..etc.) Before my waterpump went out the engine temp. guage would always stay cold and never rise above the cold range (which is normal for me) and my Path. would still be running great. Now, if it rises above the cold range I panic. When I start my Path. in the morning and turn on the heater, cold air blows out and the engine temp. rises and when it blows hot air the engine temp. falls and its like that even when I'm driving. While I'm driving my engine temp. gauge fluctuates between cold and normal (it stays hot for a while and all of a sudden it drops back to cold and it rises again, like it's confused)and it's like this throughout the course of my driving. What could be the cause of this problem?  

Answer
Bryan,

Yes, there is trapped air in the system.  Loosen up the heater hose at the engine between the firewall and engine and let the trapped air out.  Do this when the engine is warm but not too hot because when the hose is loosened up the air will come out fast and it will be followed by coolant.  When there is no air present, and it will be quick, tighten the hose back up.  Now this might take a couple of times to get all the trapped air out but it does work.