how can i purge my cooling system in my 03 nissan 350z the heater doesnt blow hot air from couple months ago but today my car stated overheating im confused idk what it could be a bad thermostat or just air in my cooling system

 

Is your coolant level good?.Does your thermostat open?.You can try bleeding the coolant system by removing your rad cap and running the car until you see all of the air bubbles come out.Thats the cheapest but messiest way to bleed your coolant system.As far as the over heating g do your cooling fans come on?.Do you have access to a scanner to see what temperature your engine is running at when the thermostat opens and/or when your car cooling fans kick in? Unless your thermostat is staying stuck closed Or blocked it won't cause you to over heat.For the no heat you can always try back flushing the heater core.Sometimes that works.
Hope this helps

 

Did you do anything to the coolant system a couple months ago prior to it not blowing hot air?

 

i just filled my reseivor tank like 3 weeks ago and that it 🤔

 

...Did you do anything to the coolant system a couple months ago prior to it not blowing hot air?