Okay guys, Here's the deal. I have heat but, then I don't. Last year I went Through winter without heat. So this year I've tried to fix that problem.
I have replaced the thermostat, heater controll valve and heater core, with a little bit of success. The problem is when I'm on the road driving and the RPM's are between 1500-2000 I have heat very hot at that, but when I stop or slow down my heater starts blowing cold air of course the outside temp. is about 27 degrees. Also I've checked to see if the fresh air vent is opening and closing, works great......

SO GUY'S ANY IDEAS.......

 

I had the same problem too. All you need to do is jack up the front (just the front NOT back), put it on jack stands, open up the radiator cap, start your engine let it runs idle, turn on your heater to the highest setting, then make sure the heater core in/out valves are openned. If not then pull one of those air pressure valve that control the water path in/out heater core. This is important, make sure the heater core tubes are NOT blocked while you're performing this task. Just keep your engine running 30-50mins until no air bubbles are left. Adding coolant if needed.

 

your saying i have air in my coolant system......i thought that the ten mm bolt on top of the manifold system was the bleeder for that of course i tried that and it didn't work but.....

 

try to bleed the air like bvtran said. after i changed my water pump, i just ran the car with the coolant cap off and topped off as necessary. took about 15 minutes.

if that doesn't work, then you can try replugging vacuum hoses at the heater valve at the firewall in the middle. i think there are two vacumm hoses. mine were switched.

 

thx guys i will give it a shot........

 

It would have been helpful if you had returned and posted the outcome of your "shot".

 

dude hasnt been on in over 2 years, he cant hear ya

 

IF you have heating/cooling problems with your car, bleeding the coolant system as mentioned above is the FIRST thing you need to do.
Kudos for searching for your problem, but realize a lot of people register and come on here to fix one thing and then you never see/hear from them again. You'll see a LOT of dead-end threads like this out there with no feedback on fixing the actual problem.

you'll also find a lot more threads that have results but don't show up in the search. :shrug:
it's a catch-22 around here.

 

idk.. but i heard this is a common problem on the maximas.. lol