I don't know why but whenever I drive and I stop (at a light or something) no heat comes out of the vents.

I have a 00 SE with manual controls. Whether I set it to recirc or not it does not make a difference.

The car operates perfectly fine (no overheating or anything) so I don't think its the thermostat. When I drive the heat comes out perfectly fine....

The only thing I recently (month ago) did involving the heat is put in 2 filters (in cabin air filter), but I don't think that would do it as it would just slow down the air (not cool it!)

 

Nissan t-stats typically fail open so they tend to allow for OVERcooling when they go bad.

 

Sounds to me like you may have some trapped air pockets inside your heater core. You should try bleeding the cooling system with either a funnel type bleeder or an actual cooling system vacuum tool that we use at the dealer.

Is your coolant level full? Doesn't really sound like a bad Tstat if heat works when you have the engine revved up and only blows cold at idle...

Also check your radiator cap for any swollen rubber seals. Maybe pressure test the cooling system when its cold just to make sure you don't have any leaks.

 

With the engine running did you "crack" the bleeder screw and check for coolant and not air there? I would remove and check that the coolant control valve isn't stuck open. If the coolant control valve sticks open it may be causing the mixing of cooler coolant from the block with the hotter coolant from the heads flowing to the heater core under some conditions like idling and at low power. (I edited this because I had a look at the coolant flow schematic and I had to rethink my original idea).

 

Had the same problem a few weeks ago. Turned out, it was just that i was low on antifreeze. Check your antifreeze levels, and also check your carpet under the passenger side dash. If wet, your heater core could be leaking.

 

you guys think I should change my coolant? I am not even sure the last time it was done...

 

Since he said that the heat comes out perfectly when moving it sounds like the only airflow he is getting is from forward motion of the car.

This would only work when he's not in recirc.

Sounds like nothing wrong with the engines cooling system or heater core.

Try driving with the recirc button in. If you get no heat when moving then my bet is the blower motor is not running? Or can something be blocking the motor fanblades?

 

low coolant ftw

no need to change the fluid now, just top it off and you can change it in the spring when its a little warmer out

 

We can go about this all day in different ways to diagnose the problem but in my opinion check your coolant level. If its low, topp it off and pressure check the cooling system to see if theres any leaks or maybe leaking heater core. You can borrow a pressure tester from autozone.

Can you hear your blower motor running?

 

That's most likely what it is, is just low coolant level and the system needs to be bled.

OP: do you get heat just when driving, or when revving it up in neutral as well?

 

You say, it is still blowing, but cold air? Or stops blowing? If first, check the blower motor. Can't be the leaking heater the smell would be too terrible to not to notice it.

 

blows but cold air

I need to double check on the revving and heat.. but I'm pretty sure hot air comes out when I rev.

 

If this is the case im almost sure your coolant level is low and/or air bubbles exist inside your heater core. Question is, coolant doesn't just disappear so where did it go? Have you checked your coolant level like we've all told you so?

 

The question was is the blower motor running??

Sitting still turn the switch in high and just front vents. You should be getting killed with some type of air. Hot or cold.

If you are getting air then it's definitely an issue with getting collant to the heater core (low, blockage, etc)

If no air from the vents then we are back to the blower isn't running. When you said that the car gives heat when moving it sounds like the airflow is coming from the forward moition of the car which woul;d happen whether the blower motor is running or not.

Let us know about the blower.

 

He just wrote the blower works fine, just blows cold air.

 

When I rev, heat does come out... then I release gas and it becomes cold again

any ideas?

 

Have you checked coolant level? It's most likely just low coolant, and an air pocket in the system. If you're unlucky, the water pump could be on its way out.

 

Jezzuz are we still talking about this, you need to check your coolant level like we've mentioned numerous times! Everything your describing points towards low coolant and air pockets in the system. It could be ANYTHING, water pump, hoses, radiator, cap, gasket leaks, heater core etc etc.

See posts 9 and 10.

 

How many times do we have to tell this guy to CHECK HIS COOLANT LEVEL! LOL.

 

I had the same problem in my GFs Altima here's how I fixed it park on a steep incline let the car cool down take the radiator cap off and start the car watch for bubbles comming comming out and once they stop comming out top off the radiator and make sure the overflow tank is full and you should be good to go.

 

Good idea. Its a pain in the a$$ bleeding altima cooling systems especially the heater core, you can hear the coolant all spashin around inside the core.

 

lol will do when its not snowing out haha!

 

It only takes 30 seconds

 

wow after all the help these guys have givin you post after post you have the nerve to keep asking for help when you havent even taken the iniative to check your coolant like they said... there offering you help so take it.... imho

 

A thread was revived 10 months later to call out an ignorant guy? Seriously?

 

Thanks jerk....

The fact that I was in philly and my car was in NY could have had something to do with it...

but way to bring up an OLD thread


btw i did add more coolant and all is good now