i have no / little heat at idle or low speeds / coasting down hills.

i have A. a new thermestate B. my fluids are good C. i burp it often.

to add to the issue - when idling or accelerating - i can hear a LOUD gurgle or WOOSH sound of God knows what liquid. like a toilet flushing. I checked my caps & none of that milky residue.

this is weird. !!!!!!! very weird. its getting to be the cold months, so it'd be nice to have heat while i get he snow off the car.

Snowmann

Burp it often? Do you have a leak? Does your car reach and maintain operating temperature as best you can tell with your temp gauge? Did you use the correct thermostat from a reputable brand?

Sometimes you gotta give the whole coolant system a shake down. New hoses all around, new water pump, new thermostat, sometimes a new temp sensor. Go OEM for temp sensor. Go reputable brand for thermostat and be sure to use the OEM type, not an "upgrade". You'd want to flush out the heater core and radiator with pressured water like from a hose or something.

Anyway, gurgle sounds require air. Do you burp using an air bleeder screw or are you on tilted ground and using the rad cap or maybe a bit of both? A bit of both is best. This is likely your issue and your sollution, so I'd start with this.

Here's a video that adresses bleeding and gurgling... I didn't watch the whole thing so let us know if it is helpful or not.
https://www.youtube.com/watch?v=t4Z25Jp3Ixc

Welcome to NICO Club! Let us know if you need further assistance. Ooh, and check our link for the FSM. That is a plethora of knowledge! Here is a link to the coolant chapter. Good luck!
http://www.nicoclub.com/service-manual? ... 0Altima/CO