Hey there, that is pretty much the symptoms, if I go and warm up the car in the morning, it doesn't matter the engine temperature, it can be completely at operating temp and it still blows cold, until I bring up the rpms to about 1500 or just start driving. When I am driving it is fine and blows warm, but when I stop at lights it blows cold again
Let me know what you think
thanks

 

prestone flush. prob clogged as hell and no coolant is getting through until the higher rpms push it through. better do it now before it becomes a blockage and a flush is no longer an option.

 

1) start by verifying that the heater core valve is opening. if it opens then

2) purge any air from the system...
http://forums.maxima.org/showpost.ph...2&postcount=14

3) if that doesn't work you probably have a clogged heater core and a "standard" chemical flush (just pouring stuff into the radiator) probably will not fix it...
http://forums.maxima.org/showpost.ph...6&postcount=44

before you tear out the heater core though, your could try to open the heater core lines and attempt to directly force flush it with a high concentration of the flushing chemicals. it might work, but I think your chances are low.

whatever you do, follow this advice (esp coolant type and purging air) ...
http://forums.maxima.org/showpost.ph...4&postcount=45