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2004 Altima 2.5L - Low heat/no heat at idle - Info Thread Forums > > 2004 Altima 2.5L - Low heat/no heat at idle - Info Thread 2004 Altima 2.5L - Low heat/no heat at idle - Info Thread
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Old 12-30-2019, 03:21 AM
ChrisWhaaaat ChrisWhaaaat is offline
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2004 Altima Sedan
2004 Pathfinder
Join Date: Dec 2019
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Default 2004 Altima 2.5L - Low heat/no heat at idle - Info Thread

Hey Folks,

This thread is meant to provide info/my experience regarding a problem I've encountered with my girlfriend's 2004 Nissan Altima 2.5L and the simplest solution I used to address the issue. It should apply to any 3rd Gen 2002 - 2006 with a 2.5L, but more broadly can apply to almost any car. IF YOU ALREADY KNOW YOU JUST NEED TO BLEED THE AIR, SKIP TO THE PROCEDURES/STEPS SECTION

The following text is to provide context on coming to the conclusion that air should be bled from a system and is geared toward entry-level inquiries.

We've had the car for a year. Bought it during the winter (in Canada, it cools off pretty good where we are). It blew heat all the time, no noticeable issues (other than a poorly functioning fuel-gauge but thats another story).

This winter, I began to notice a lack of heat at idle/when sitting at lights... then while trying to warm it up/defrost windshield prior to driving. It blew heat fine while driving, had heated seats, so we just started parking it in the garage overnights and were none the wiser. But on some cooler days, especially in stop and go traffic (lets face it, mostly stop in the city), it got pretty cool sitting in there.

Here is what I knew, based on the symptoms:

- The car is not overheating, therefore the thermostats must be working (I understand there are 2, separately located)
- The heater-core, fan, and dash switches have not failed, since it blows very hot while driving and no variation in fan.
- The coolant isnt leaking - but it was slightly low (reservoir empty, rad full). This was my hint that maybe some had disappeared or there was air involved.
- Some notice an occasional "Whooshing", splashing, trickling/running/pouring water sound coming from the passenger side dash. I had a very slight amount of this, but not much.

Given these symptoms:
- Higher revs increases circulation in the cooling system, therefore pushing air bubbles around in the system. When the pressure and flow drop, the bubbles "settle" right back into the same, high place. Unfortunately, that highest point is the heater core.

So I need to try and bleed/kick the air out of the system.

You will find numerous ways to do this posted online. Some are simple, some are hard, some are vehicle specific, some require special tools.

Frankly, there are a few of the methods that either A) Don't make sense to me, how the hell do they work, and B) just dont work, because they're wrong.... Anyways. Im not a mechanic, but I work on my own and family's vehicles regularly, so felt this should be an easy thing to address myself. (Again, I am not a mechanic, this is simply a record of what I did).

If you own a jack, vehicle ramps, or a steeply sloped driveway, you can probably manage this 'repair' without buying anything, which I did.

****If you are working on your own vehicle, please for the love of god work safely. That means PPE as required. WEAR SAFETY GLASSES. You can burn your hand off and get a replacement but if you lose your eyes, its game over. Since there is coolant involved, and it could be hot, wear gloves and cover all your skin just in case. Also, use jackstands (do not let vehicle sit on a jack) and/or chock your wheels depending on your method of choice, and apply your parking/emergency brake. *****


1. Start with the vehicle cold.

2. Lets assume you have already checked that your reservoir tank, coolant lines, radiator and coolant system are not leaking. You have also checked your rad (cold) to see that it is full of fluid, and that you have been able to achieve all the other conditions i outlined above with heating, cooling, etc. If you have not, address them first (eg: filling reservoir if its empty, top off rad if empty, operate vehicle, make sure fan is working).

Raise the front end of the vehicle off the ground (I read approximately 2 feet). The goal is to get the highest exit point for the air above the heater core. 2 feet gets you roughly there. You can accomplish this with tall ramps, blocks and a slopped driveway, or a 1-2 stage lift with a floor jack, or an automotive lift.

3. Give the air somewhere to go. You can try this by just removing the rad cap altogether, and leaving it off and just running all the procedures that way, then manually topping it off. BUT, you will likely find its harder to tell if anything is going on, and are more likely to spill coolant or have it splash out of the rad. To make my life easy, I did the following (which is often recommended)

4. Remove rad cap (this step can vary). Use a bent nail, wire, or whatever thin and somewhat flexible piece of metal rod or wire you desire to pin the inner part of the cap to the open position. Some caps have a stem that protrudes from the inner cap, and some do not. In my case I bent up a piece of tie wire and rested it in the rad opening (pictured below). It doesn't need to be thick, the cap still needs to fit on. After you've inserted this wire spacer, put the cap back on.

5. For me, None of these fancy hoses, adapters, clear hoses, funnels, or any of that crap. There is a perfect hose and clear container already attached to your radiator. Its called the coolant reservoir. Remove it (2x 10mm bolts), hang if from the hood such that there are no high spots in the line, and that you can see it from inside the car. (picture below). Make sure it was full of coolant to the max line when still installed before hanging it.

6. This procedure can vary, again, but I went with this: Turn the car on (engine running). Let it warm to operating temperature (needle roughly at middle of temp gauge). Turn on the heat, max heat, max fan, air flowing through car not recirculating. A/C on. Let it run like that for a short bit (This isn't exact, maybe not required). Its now been about 3-10 mins, depending on the conditions.

7. Get in the car, observe the coolant reservoir, the fluid level should be pretty calm and steady. begin to rev the engine up slowly and steadily to between 2000-3000rpm. Try to keep watching the reservoir. You should see bubbling or disturbance of the surface of the coolant (should look like its bouncing around). It might not be significant, but if you hung it nicely, it should be pretty still otherwise. Hold the revs at 2000-3000 rpm for anywhere from 10 seconds to... however long you want. I did it for maybe 15-30 seconds each time? I stopped when the bubbles (which I couldnt quite see) stopped bouncing the coolant around. It can be pretty subtle. I repeated this 4 or 5 times, waiting for maybe 30 seconds between cycles. Probably longer, as I was 'feeling' the cab heat for improvements in between. After several cycles, It appeared to have slowed in terms of bubbling, so I let the car idle for 30-60 seconds after i decided that was enough for that cycle and then shut it off (along with the heat and fan off).

8. You will (maybe) notice a small (or large) drop in coolant in reservoir. Thats okay, it means coolant has replaced some of the air in the rad. (If you run out of coolant during the previous cycle, stop performing the cycle and refill your reservoir). Mark the reservoir if you wish before leaving, so when you come back you can tell if the level dropped at all. Or if you have a better memory than I do, dont mark it. I noticed about 1/2 quart/litre drop when I returned.

9. Let the vehicle cool off for XX amount of time (till the rad has cooled. I used a small fan in my 0 degree celcius garage to cut my time down to 30-45 mins).

10. Check reservoir, top it off to max, then repeat the cycle again as required. On my second cycle, the air stopped disturbing the surface of the reservoir coolant quite quickly, and heat had returned to the vehicle's interior at idle, so I stopped.

11. At the 'end' of your cycles, let the vehicle cool fully. Re-install the coolant reservoir back in its home. Top it off if required to the max line. Now with the rad (COOL TO THE TOUCH), remove the rad cap and pull your wire/nail/whatever you used) out and reinstall the rad cap. Assuming you now have heat in the cab (you will be able to tell during the cycles when the vehicle is at idle), your vehicle issue should be solved.

12. Lower your vehicle, remove safety devices as required. Clean up and responsibly dispose of any spilled/excess coolant. Wash your hands, dont lick the glycol off your fingers when you're having chips later. Even if you wore gloves.

This method may help return heat to your vehicle at idle. It may not solve the original problem that caused the air to get in there. Though, in the case of the altima, it appears to sometimes be due to a manufacturer issue that they have indeed acknowledged (there is a service bulletin for it). You might have other causes for the air infiltration/loss of coolant including incorrectly performed coolant system flush, bad heater core, failed head gasket, other leaks, empty coolant reservoir. This method may get the air out, but the fix could be temporary, or it could be permanent.

I chose this method because I could do it without buying any tools/vaccum devices or jerry rigging any funnels and hoses.

Please dont work on your vehicle unless you feel comfortable doing so and feel that you have the knowledge to perform procedures safely and correctly. Consult a service manual or mechanic for the most accurate information.

I hope this helps. I've probably missed something but I'll try to check back and edit as required. While I realize this is a repeat of other threads ive seen around online, I didnt find any that explicitly listed the information in this way, and its the information I wish I had been able to find the way I wanted it in the first place.

All the best to those wrenching at home,

Attached Thumbnails
2004 Altima 2.5L - Low heat/no heat at idle - Info Thread-img_6167-jpg   2004 Altima 2.5L - Low heat/no heat at idle - Info Thread-img_6168-jpg   2004 Altima 2.5L - Low heat/no heat at idle - Info Thread-img_6169-jpg   2004 Altima 2.5L - Low heat/no heat at idle - Info Thread-img_6171-jpg  

Last edited by ChrisWhaaaat; 12-30-2019 at 03:23 AM.
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2.5l, altima, heat, heat/no, low

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