2001 Pathfinder Over Heating!? Insights PLS!

[HankyD]

Hi guys,

I have a 2001 Nissan Pathfiner with approx 270xxx km / 168xxx miles on it. I was going about my regualer routine which includes a lot of stop and go driving. I had the AC on all day cuz it was warm out... and at 3:00pm while I was in traffic, I noticed that my Pathfinder was starting to overheat. In fact, it wasn't long before it got way up there so I began to worry. I quickly turned off the AC, cranked the heat and rolled down my window. When it was time to move, I did so gingerly and my truck cooled down. I continued with my routine which dragged on until about 7:00pm that evening, the whole time with my AC off, heat cranked and window down. Since it initially happened at 3:00pm, it never happened again that day.

I tried to mimick the same thing again just yesterday, but I couldn't get it to happen. I had the AC on and took it for a spin including up hills, stop lights/signs, the typical. To no avail.

Here is what I know after doing some investigation.

i) No coolant leaks anywhere and no puddles anywhere. No unusual sounds or warning signs from underneath the hood.

ii) Fan clutch... seems to be in perfect shape. No free lateral movement and no extra revolutions/free movement when trying to spin the fan with my hand. Fan comes on when I turn on the vehicle and blows a lot of air through the radiator.

Because of these two things, I am thinking that I can probably rule out both the fan and waterpump.

iii) No debris infront of the AC exchanger or radiator. Everything is clear of debris.

iv) I was thinking thermostat... but I heard they seldom fail and when they do fail, they typically fail in the open position and not the closed position? If it were to fail in the close position, I would be getting overheating a lot more frequently wouldn't I? At operating temp, my upper rad hose is hot and my lower is cool...to me that means that I have hot leaving the engine and cool leaving the rad.

v) Radiator - Could my radiator be plugged up? Or at least getting plugged up? I do have quite a few miles on the thing. Would flushing it out help unplug it from any potential debris? Or at least worth a shot?

vi) Cap... I have inspected it and it looks fine. But it's a cheap fix so maybe I will just replace that to rule it out.

vii) Pressure test - I have not conducted this cuz I don't have the equipment. I know that this is usually the first step in diagnosing overheating/cooling system issues.

viii) Air bubbles.... if it is, I don't know how they could have got in there lol Unlikely in my estimation.

ix) Coolant.... is now brown due the the over heating experience of this past Friday. Clearly I should get it flushed.


I guess I am leaning to a plugged rad/partially plugged rad ... but could my fan clutch be acting up even though it appears fine upon inspection? Not pulling in enough air while the AC was on in traffic might have done it obviously.

Anything insights provided would be appreciated,

-h

[Buzzman]

Definitely start with a flush. Brown is not the desired colour....lol.
My 2002, with 295,000 Kms., overheated earlier this year.
Replaced the rad, old hoses, thermostat, and it's been fine ever since.

[atraudes]

The coolant color makes me say also check your oil. If it's milky at all, it means you have coolant and oil mixing which is much bigger problems.

Otherwise, your initial analysis are my thoughts as well. Let us know how it goes and what you find!

[HankyD]

Update:

Well, I flushed out the rad last night. The fluid wasn't super brown, more like an olive green, faded an discolored.

I don't know how much fluid the rad holds... but to be honest, it didn't seem like much at all really. Before I flushed it, the rad was full too by the way. Also, the core inside the rad..... looks pristine! Like brand new. I can see the metal finish and it looks perfect, not corroded and rusty at all.

The oil... is fine too by the way, not cloudy or anything.

I guess we will see what happens? Any thoughts?

-h

[HankyD]

UPDATE

I had to bring it to a mechanic because the overheating got worse the on Monday despite giving the system a flush over the weekend.

The culprit was (drum roll pls) the 2nd thermostat right next to the firewall.

The first time I've ever had a thermostat go bad on me. Doesn't sound like a loceation in the engine bay that I would want to tackle.

Thanks guys,

-h

[towncarblue]

wait... that thermostat is only there to warm up the engine quickly to the operating
tempature. when the engine is cold the thermostat is open, when the engine reaches operating temp the thermostat closes.
i dont think it would matter if it stayed open , it all loops through the radiator.
i could be wrong though

-air bubbles are very likely , due to engine design. that's why nissan put a air bleed near the firewall
-just looking though the radiator opening is not gonna tell you if its clogged.
-i thought the fan clutch was supposed to spin freely when the engine is cold?
-did you open the air bleed located near the firewall ??? when i did a coolant flush it took alot { about a gallon and a half } and then some more.
-according to the nissan factory service manual its Coolant capacity (Without reservoir tank):
 9-1/8 quarts { Ma-16}
-if your main thermostat is working {should be the first thing you replace anyway} then you have an obstruction somewhere or the water pump is
done. your coolant is not cycling completely .