I have an 04 g35 coupe, 75k on the clock. When the car is warmed up I do not get any heat from the vents unless the car is moving. I searched this issue & 9/10 threads indicated its air in the system. I checked the fluid level & all is well. I removed the radiator cap, resevoir cap & started the car. I put some fluid into the radaitor using a funel with fluid stacked in the funnel. I removed the bleeder screw from the heater core line towards the back/passenger side of the engine bay and after 15-20 minutes fluids ran out of the heater core line. I reinstalled the plug & left it loose & let the engine continue to run. I did not see any more fluid pushed out of that plug unless it was fully removed. I did not see any air hic-cup in the funnel @ the radiator cap so it seems to be ok however the next morning after the car was started & warmed up there was still 0 heat from the vents at the highest setting. Once the car moves a bit there is plenty of hot hot air.

Its getting colder & colder each morning here & this is my DD. I planned to get a remote starter installed for this winter but if the car dosnt actually heat up @ idle its kind of pointless.

The issue is still occuring even after bleeding the system so I am at a loss as to what could/may need to be replaced. A dealership said its probably just the thermastat & those are cheap so I may just swap that out this weekend but wanted to check in before I just go around changing parts. I was under the impression that if the thermastat was stuck open the engine would take longer to warm up and it seems to be at the halfway mark on the engine temp within 10 minutes of starting the car. If it were stuck closed wouldnt the car be having over-heating issues?

I am open to suggestions at this point. I would prefer not to take it to a stealership at this point but am on a bit of a time crunch given my work schedule.

Thanks for the info as always!

 

Went ahead & ordered this


Ill re-bleed the system & probably go ahead & change the thermastat this weekend. Its only a few bucks and is easy enough to knock out on Saturday. Ill post up if that corrects the issues im having

 

I am not sold on the thermostat suggestion by the dealership, based on your comment the temp gauge is reading at the halfway mark in ten minutes which tells me the T-stat is doing its thing. What happens when you select front window defrost? Do you get hot air from the defrost vents? It almost sounds like a plenum door valve is sticking and opening when the car moves.

 

I just did a little reading, there is a Self Diagnosis Function you can perform to help you troubleshoot. It is located in the Automatic Air Conditioning Section (ATC) of the Service Manual, this same section shows all the ducts and doors in the system.

 

What kind/color of coolant did you add to the car? It's possible that you added the wrong/incompatible coolant type of coolant. If you mix Dexcool with Ethylene Glycol coolant, it will get all crystallized and gum the $hit out of your cooling system. Our cars take Ethylene Glycol based coolants. If this happened, it might have caused enough of a blockage in your heater core that it only flows when the water pump is moving at higher RPM's.

How much coolant did you have to add when you filled it up?

Take your radiator cap off when the car is cold, and look inside to make sure everything looks OK and it doesn't look like Superman's fortress of solitude.

 

Thanks for the info

-I can check the defrost vents when I leave work today. Do you mean to just see if it gets heat when moving from those vents, or at idle once its warmed up? I definitely get air from those vents but never really paid attention thus far to see if it gets cold at idle like my normal vents. I can find out today

-I added 50/50 premixed green prestone coolant. It took less than a cupful and most of that was because when I opened the heater core bleed screw completely and the car got warm enough some fluid was pushed out of the hole. The reservoir was just a hair under the full mark to start with. I had the bleeder screw just loose for a while but it wasnt pushing fluid out at all until it was removed entirely. There is a oring seal on the screw/valve that prevents any fluid from getting past unless its basically completely removed so i just pulled it & let it run with the rad cap open & a funnel+fluid to keep it full as some fluid was drained out via the valve.

-The coolant looks ok, its just green as usual, nothing out of the ordinary in the radiator or reservoir.

-Yes even on a cold morning by the time I have driven aprox 10 minutes the car is at normal operating temperature. No over heat issues & it seems to get up to temp at a normal rate.

-I will look into the Automatic Air Conditioning Section test. I presume this test is for the vents to make sure they are opening/closing properly? I will note that my a/c works great. My heat does work just only when moving. Once I hit idle its just warm at best within 5 seconds.

 

if you rev the engine and hold it at say 3k rpm, does it still blow cold air or will it kick out heat? If it blows warn when not moving but holding the rpm up then its most likely something to do with your coolant and circulation.

Do you have your fresh air on or on recirc? I dont know exaclty how our HVAC is routed, but if your fresh air is on depending on where the door is located it could be why you feel heat when moving.

 

Yes the Self Diagnosis Function Test checks the door operations, for my year car it starts on Page ATC-56. A couple of my responses are in the Quote field above.

 

I have an 06 sedan that is doing the same exact thing. I have bled the system more than once but I know there is still air in there because I can hear it sloshing as it goes through heater core. Today I am going to take a mechanics recommendation and jack the front end of the car up while bleeding the system. I use one of those spill free funnels which seem to work pretty well. I will report my findings as to whether this fixes the problem. Kevin

 

O.K. preliminary tests are complete and it appears that I have heat at idle! I put car on ramps lifting up front end and used spill free funnel (If you do not know what this is you can find it on youtube) which to me is the very best way to bleed this God awful cooling system. It took quite a while to get the "burps" out of the system. As the system burps out the air it takes in the coolant from the funnel. I think I added about 12-16 oz of extra coolant after air was released. Next very cold day will have final test.

 

To be honest, I havnt gone back and done anything with mine yet. The weather has been decent and ive been out of town for work the past few weeks on weekends.

I have bled the system for an hour 3-4 times and it hasnt done much. I can throw the car on ramps but I am going to swap the T stat this weekend either way. I finally have a weekend with free time.

My issue is a flow issue. If i keep the rev's up the car blows hot air at idle. Once the idle drops to normal the heat is gone until I rev it or get the car moving again. Ill swap the T stat and re-bleed this weekend. If the issue persist ill take it in to have them look at it, I just ordered some new bushings, ball joints & struts so ill have plenty to work on this weekend either way. I didn't forget to update this thread, just haven't had the time to put into the car. Ill update after the weekend. Thanks

 

O.K. I am not certain but I hardly believe your thermostat is the problem. Why? Because I had the exact same symptoms. Once RPM's are at 3K or better the heat flows fine. Come to a red light and it gets cold as a cucumber. There are air pockets in the back of the system.(In heater core) I bled mine twice for about half an hour and each time I got air out but it still would not get heat at idle. An Infinity mechanic told me to raise up the front end. I did and got a lot more air out and as for now when the car is at idle the heat is working fine.(This took at least 30 min of on and off revving, you have to rev it up then let it settle to bring bubbles up) If you use the spill free funnel you have a much better advantage bleeding the system. #1 you know exactly how much air is coming out by the size and frequency of the bubbles. I observed one of two ways, either having my daughter raise RPM's while I stood at front of car or by sitting in front seat and looking at the "shadow" of the coolant in the funnel. I can see the level and when it bubbles the shadow "moves". #2 You can see exactly how much coolant is sucking into the system as the air bubbles out. I will be curious to see if you follow these directions if it does not resolve your problem. If it sucks in coolant you know that is all displaced air.
Kevin
P.S. I used the incline of my drive way (back tires in street, front on drive) plus the ramps to get the front end up a little higher.

 

All right ill give this a shot. Were you also opening the bleeder valve in the back? My issue with opening that valve is once it starts to really flow coolant it just dumps it down on the exhaust.

The G is actually too low for my ramps lol. But I have several race jacks I can use to lift the front end plenty high . I have a spill free bleeder kit so no worry's there. Ill give that a whirl this weekend and see if it makes a difference. Thanks for sharing!

 

this may sound dumb, but mine needed a new cap on the Rez.. no ****ing clue why this fixed mine since the rez is not pressurized.

 

No I used it once and it gets rid of very little air compared to the funnel and like you said makes a terrible mess.