Weak Heat at low RPM's

[oreogaborio]

Wondering what could cause my heat to blow cool air at sub 1.5k rpms.
Coolant is topped off, no leaks as far as I can tell

Anyone else have this issue in the past? What's the fix? Does the system need to be bled? Heater core on its way out?


EDIT: Did some reading and it seems I need to bleed the system by either finding the bleeder by the firewall or jacking up the front of the truck while it's running to get the air out.
http://www.justanswer.com/nissan/2v43d- ... nning.html

Can anyone confirm?

[mar1]

check these:
http://www.thenissanpath.com/viewtopic.php?t=2504

and thenewX has a decent writeup to do the "burp":

http://www.thenewx.org/forum/showthread.php?t=24370


it could also possibly be the thermostat is stuck open, have you checked that?
http://www.courtesyparts.com/21200-ther ... =6833_7702&

[oreogaborio]

Thanks for the links. Looks like I've got to burp the system.
Thermostat should be good. It's coming up to temp quickly. Only symptom is cold air at idle.

I did notice the rear heat isn't working very well, either... Hopefully burping the system will iron that out, too.

[pgleduc]

I seem to have the same problem with air in the cooling system and no / or very little heat. Checked all systems, tried burping the pathy twice (with raised front end method) and even flushed the system (followed by burping again) but to no avail.

I note the other method (the one posted in thenewnx forum) works for some R51 Pathfinders but there is no nipple / bleed valve by the heater core in my 2009.

Can anyone point me to the location of the bleed valve?
Thank you

[mar1]

I seem to have the same problem with air in the cooling system and no / or very little heat. Checked all systems, tried burping the pathy twice (with raised front end method) and even flushed the system (followed by burping again) but to no avail.

I note the other method (the one posted in thenewnx forum) works for some R51 Pathfinders but there is no nipple / bleed valve by the heater core in my 2009.

Can anyone point me to the location of the bleed valve?
Thank you

check your thermostat

[pgleduc]

Yes, I thought of that but as the vehicle comes up to normal operating temp quickly, that doesn't appear to be the issue. But I guess I don't have much to lose by checking the thermostat.

That said, I would still be interested to know if there is a bleed valve in the cooling system.

[oreogaborio]

Burped it.
I now have great heat at idle.
Rear heat is still weak but I THINK it's a little better.

What do I check next? Comes up to temp quickly.

[disallow]

burp again.

The lines in the rear are higher than the engine. Really hard to get the air out of them.

When I had this issue, I added almost a gallon of coolant. One would think I had a leak on my hands, but since then it has never lost any coolant, and that was over 3 years ago.

[oreogaborio]

Wow, no kiddin? I added a good quart and a half.

Aight, I'll give it another go.

[oreogaborio]

Burped again. It did take more fluid and the rear heat started getting warm"ish"... but still not blowing very hot.

Process:
Put the truck on ramps
Stick a bottle in the radiator cap (see vid. Uploading to YouTube)
Fire it up, rev it a bunch of times, let the bubbles come up & refill.

That's really it, right?

http://www.youtube.com/watch?v=n0MkFBDyEUc

[disallow]

Heat on full blast as well.

[NVSteve]

I had my 60k service done a couple months ago & draining/replacing the coolant was one of the service items. They obviously did not burp my beast afterwards because I'm having the same symptoms-low to no heat at idle, hot when driving. I didn't notice it until this morning when I needed the heat on, so I guess I'll take it back in and have them burp it. If they fail at that, I'll do it myself, thanks to all the info in this thread.

[glockshooter]

Hey guys, I checked this out on my 07, I found the fitting, but it doesn't look like the ones pictured. I don't have the top T fitting. Am I limited to just getting the front end up and opening the caps?

[CDUB]

I found this awhile back while on youtube looking at people's cross contamination issues with the coolant and atf. Kind of an "out there" approach at burping the system but it seems to have worked fine for this guy. Here is the link http://www.youtube.com/watch?v=n0MkFBDyEUc . Also i'm almost sure there was some of a messy clean up for this guy when he took the bottle off the system, but if it works, it works.

[jambo56]

The easier method I have found to bleed the cooling system on a 2011 Nissan Pathfinder:

1. Remove the radiator cap. You will see it has no valving, it is simply a cap.
2. Pour coolant into the radiator until the level is just under the overflow outlet line to the reservoir tank.
3. Squeeze the return hose to the radiator several times. This will burp a few bubbles out of the top of the radiator.
4. Refill the radiator as in step 2.
5. Replace the radiator cap.
6. Remove the coolant reservoir cap. You will find the reservoir cap holds the pressure valving for the coolant system.
7. Fill the reservoir will coolant to the "MAX" line.
8. Start the car. Set front and rear heaters to high on temperature.
9. Take some coolant with you and drive the car for 10 minutes or so, on smooth roads. This will keep from sloshing the coolant in the reservoir.
10. Stop after 10 minutes. Check the coolant in the reservoir. Add if necessary.
11. Drive the car another 10 minutes.
12. Again check coolant and fill as necessary.
13. Replace cap on reservoir.
14 test operation of heaters at idle. If condition persists, check the heater water pump located on driver's side firewall.

This basically bleeds the system with no mess. And since you are driving the car, you are supplying enough RPM's to spin the water pump hard enough to force coolant everywhere. The radiator cap, since it has no valving, allows the trapped air in the system to bleed through the radiator overflow hose, into the reservoir. The air is expelled out of the open cap from the reservoir.

I did this when my 2011 Pathfinder had problems with no heat while idling and heat when driving. After this procedure was complete, the problem was solved.

No muss no fuss.