I've been trying to look up another solution for the problem on my altima but so far nothing that's been suggested worked. Ever since I had to replace my radiator i had no heat at idle. At first I had no heat at all until I burped the coolant and replaced the lower thermostat. Now I still have no heat at idle. I've tried to burp the system again after draining it and no luck. Recently I purchased both upper and lower OEM thermostats from Nissan and replaced both of them. Is there a way for me to test for a faulty heater core without removing it? I'm going to try to flush it out tommorow but I feel like that won't change anything at this point.