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Discussion Starter · #1 ·
Hey Everyone,

I'm lost at this point.

I love our 2007 Armada SE - so much I've spent hours trying to get to the root of its overheating problem, which isn't consistent.

The story so far...
I've replaced the radiator, top and bottom hoses and thermostat.
Checked several times there are no leaks, or trapped air bubbles.
The AC pressure checks out great, and blows ice cold except when the gauge passes the 75% mark.
Self-diagnostic produced electric fan coming on all 3 times without fail.
Jumper leads to fan also activated the fan without and issues or delay.
Clutch fan tested fine, with proper tension.

Here's the thing. Sometimes it overheats, sometimes it doesn't. I just sat in full stop traffic for over 20 minutes and it didn't overheat. Two nights ago I was sitting idle and in park and it overheated within 10 minutes. I noticed the electric fan comes and goes intermittently, regardless of AC, regardless of temperature. In fact, when the engine temp rises at all, the electric fan never turns on.

I have tested the relays and their resistance checks out. I just don't have anything consistent to know when to check for clicks or voltage. Odd enough, the other night I pulled the 10a relay fuse because I couldn't get to it to see and my multimeter reported 0v
As soon as I pulled the fuse, the electric fan came on (??) and the 4WD light on the dash. I plugged the fuse back in and the fan continued to operate for a few minutes. The light eventually went away. Since then, the electric fan has been active more often but still intermittent at best.

I have not tested any part of the coolant temp sensor. Not sure if that's at play. Not sure what else to test. Water pump seems fine. The belt and/or tensioner pulley do squeak a little when it's cold.

So with all that, I'm lost and need some advice.
 

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heater core?
sensors may be faulty?
water pump?
wiring issues causing loss of continuity. if wiring gets hot this can perhaps loosen up something to make things work temporarily.
if heat inside engine room gets hot enough, clutch fan should come on regardless of AC. even if the car sat outside on a hot day and the temps inside the engine room got up to a certain point, once you crank up the car the clutch fan should run for a few seconds at startup.
if none of that is happening, you may have some wiring/temp sensor issues.

i've attached a couple of nissan service manuals that may help in case you don't have them.
 

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im not a mechanic, just been around these forums for years and have seen similar issues so just trying to help.

if the clutch fan is constantly running, that could mean the fan is faulty. when the car is off and the engine room is cold, the fan should spin freely by hand. if its still "engaged" (e.g. difficult to turn by hand) that may signify a faulty fan. just my opinion.
 

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If all the mechanical functions are working then it’s likely air still trapped in the system.
When the radiator and related parts were replaced, did you burp the air out by leaving the radiator cap on and with the pressurized reservoir cap off?
 
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Discussion Starter · #6 ·
Hey everyone, sorry for the delay. It's taken me this long to really get back into this.
Yes I did burp out all air, complete to factory service manual instructions.

Since my previous post, I've changed the water pump, and coolant temp gauge since I was in the neighborhood. I also replaced the fan clutch in case that was faulty. Finally today I replaced the thermostat again in case the previous was defective, and with a lower temp (170d) version.

After driving for about 30 minutes in 76d weather, it did start to get hot again. Under normal operation, it sits st about 40%. Today it's going between 50% and just left of the high mark (see image). It would sit at each end for about a minute, then switch.

One thing I did notice this time when watching the reservoir while warming the Armada is a bunch of tiny bubbles on the surface. Not cloudy - there's no oil in the coolant, or vice versa. The coolant is crystal clear. I'm leaning toward a faint leak somewhere that I can't see. I don't like throwing parts at something until it fixes. I'll update if anything else.

Thank you all for the suggestions! View attachment 50498

I also want to point out, sitting in the driveway for over an hour does not cause it to overheat. Driving seems to set it off.

One other thing that came to mind is this used to not happen before we started towing our RV. Is there something I could have stressed? Our Armada does have the tow package and I've been careful to stay within its limits. May be a coincidence but I figure it's all part of the equation.
 

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Discussion Starter · #7 ·
Update: when it overheat yesterday, I turned it off and put my hands all over the radiator, and felt 1 very hot area, where by contrast every other area was slightly warm to the touch.

Seems like my replacement radiator has caught a clog and is now the cause of the overheating.

In a future post, I'm hoping to share all I've learned in this process.
 

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When you do a coolant fill, make sure you have the heater set all the way. This will open up the heater core valve and you could add more coolant. Keep the heater all the way when releasing air bubbles. Burp the system with the radiator cap off while the engine is running. The coolant level will drop inside the radiator after every burp so keep refilling until it no longer drops.
 
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