The Nissan Path

Since its cooled down some and I've started needing some heat I've noticed it COMPLETELY goes cool if I come to a stop. Almost instantly, stone cold.

Could this be a thermostat issue, I appreciate any suggestions.

08 V6 by the way.

probably low on coolant. Top it up! Check for leaks!

It could be a bad heater pump. There's an electric pump near the firewall connected to heater hoses on either end. It's used to push the coolant through the heater core.

Ok, I will check my coolant level today. How hard is that pump to get to if it comes down to that?

Still no luck with this at all. Coolant level is fine. Checked it both warm/cold and even parked on a steep hill to see if there was any differences but didn't notice anything.

I'm guessing it's that electric pump mentioned which looks like it's a tear down from inside the truck. I hate jacking with heater cores too. Has anybody ever done this? I already know it's gonna be ugly. I can handle the work, just looking for some pointers if anybody has any...

cooling system may have air pockets in it
have you thoroughly "burped" it?

I'd go diagnosing step by step, but first:
- coolant level at expansion tank (to max line) and in radiator (full)
- any leaks under vehicle when running warm on parking lot?
- does A/C controls move ventilation valves (you can hear plastic clunking sound, when air ducts open and close with changing air direction up/front/down)
- does engine gets warm when driving? (temp gauge almost at 1/2 scale)
- does temp gauge fluctuate a lot when driving? Like moving up and down noticeably, where it should stand still?
- when engine is hot, try heater pipes, going to cabin at firewall. Are both pipes hot? Or one is hot, the other cold?
- find heating pump and see if it is running, when you turn heating FULL on and BLOWER on max.

This is what heat pump looks like:

I would do a good burp of the system before you tear it apart. My level was showing full before a burp, too.

Thanks guys, fluid levels all around are full even in the expansion tank. No leaks at all.

No fluctuations in the gauge when driving, it's all normal. But like I said, once I give it just a little gas (say anything above 1200rpm) it starts blowing hot again.

All the systems associated with the vents opening closing and all that work fine.

How do I do the burp deal? I've heard that mentioned a lot on here it seems.

My radiation was replaced this time last year for fear of the cross contamination issue but the heat worked fine at idle all last winter.

Thanks again, I'll keep after it.

staynlean wrote:
How do I do the burp deal? I've heard that mentioned a lot on here it seems.

You hear it mentioned because it's almost always the cure for the problem you described. I have no idea why but mine needs this every year or so. Plus, if there are air pockets in the system then you don't have as much coolant as you think. So be prepared to add coolant once you burp the system. Plus, some coolant usually spills out during this process so be prepared for a bit of a mess as well. Here's the process posted from an earlier post about this:

Start with a cold engine....don't open the radiator cap if hot!! In adition to the below, I turn my heater on max high as well as the rear heat.

drive the front up on ramps
open radiator before it heats up and the system gets pressurized
let the system warm to full temp
IIRC rev up to 2-3k rpms several times
let it idle a few moments
add any fluid if necessary
cap it and bring it back down

If that doesn't fix it, then start looking at some of the more difficult/expensive options. So far over 7 years and 140k miles, this does the trick for me every time.

The electric heater pump is in the engine compartment, on a bracket attached to the firewall. It'll have an electrical connector and two heater hoses attached to it, like the picture above.

Much thanks, going to do the burp later today and update later.

Hey, maybe I'm just blind but I do not see this electric heat pump. I don't have rear a/c, maybe that pump is only for those models?

Will post a pic later. All my hoses lead strait into the heater core, strait through the firewall. Nothing between them and the radiator.

2011 V8. Same issue. No heat coming from the vents when at idle. Depress the accelerator and heat comes back. Air is blowing through the vents the entire time, it just goes from cold to hot depending on idle RPM vs above idle RPM.

Curious if the OP ever solved the problem.

Coolant flushed at the shop via the machine a little while back but not since last winter. Not sure why the system would need burped or how it would have gotten air in the system.

Thanks

This is what I ended up doing not too long ago.

1. Buy gallon of coolant. In my case it was the blue stuff.
2. Fill up radiator all the way to the top. I rocked the vehicle side to side and it seemed to have let you some air because the level would go down.
3. Fill up the overflow tank to the top.
4. Drive around for a while.
5. Check coolant levels again and fill up as necessary.

Took more coolant this way which in turn cost a little more. Any excess coolant will spit out the nozzle right below overflow tank lid.

The burp method mentioned works as well so your choice.

With all that said, I was low on coolant because I had the lower radiator hose not quite tight enough so was slooowly dripping coolant. Tightened that up and did the above.