Nissan Repair: Nissan Quest Heatting/Cooling, coolant level, long hot summer

Question
1994 Nissan Quest.  140,000 miles.  New battery, car stored outside.  Just started a cold (high 40s F) snap here overnight after a long hot summer.  The A/C has been broken (freon leak) for a few months.  Coolant level is normal.  This morning, it followed the following cycle: after starting, the heater blew cold and the engine temp rose almost to H.  It started to blow hot briefly and the engine temp fell.  It went back to blowing cold and the temp rose.  No adjustment to climate controls throughout this time.  It did this two or three times in a 15-20 minute drive.

Answer
Pierre,

The car has an air bubble in the system.  You are going to need to bleed the air out of the system to get the car to run normal.  Basically, there are small bleeder screws on the highest point of the cooling system like where the radiator hose connects to the neck on the engine and you have to open up the small bleeder screw, with the engine running, to get the trapped air out.  Also, I have found, on the heater, I like to loosen one of the hose clamps on the highest part of the heater hose and let the trapped air out there.  You have to be careful not to loosen the hose so much as to have it come off.  And, start with a cold engine as you do not want to get sprayed down with coolant.