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Discussion Starter #1
I have a 2002 Pathfinder. I have an issue with the heat gauge when cold temps set in (below -5 overnight).
Basically the heat gauge will rise to the H and after driving for a bit (5 mins to 1 hour) it will snap back to the middle.

I did the thermostat twice thinking it was sticking and last fall I did the coolant temp sensor. I follow the temp with an OBD2 that links to my phone and temp goes no higher when its reading high then when it sits in the middle. It does seem a bit high though (110C) but I dont know if that's normal for a pathfinder.

The water pump isnt leaking and doesnt seem to be giving me any signs it needs replacing.

Any help on this would be much appreciated!
 

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NF Mod/Nissan Master Tech
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You have a coolant temperature sensor, Nissan P/N 22630-ED000, for the ECM to use for fuel management, which has a 2-pin connector. You also have a coolant temp sender, Nissan P/N 25080-89907, for the coolant temperature gauge, which has a single terminal connector. If you have gauge issues, you may have replaced the wrong part. You also have two thermostats. One is at the front of the engine and built into the thermostat housing and the other is the more conventional style, sometimes called a water control valve, located on the top side of the coolant bypass between the two cylinder heads, on the back side of the engine. If you haven't changed that one, you may want to do that. The front, or primary, thermostat opens around 76 degrees C. and the "water control valve" opens up around 96 degrees C. Operating temperature of 110 C. is on the high side. If the coolant sender is okay or new and both thermostats have been replaced and it's still running at that temperature, you may have another issue which could be a restrictive radiator or even a bad head gasket. I usually find where there's a situation where the temperature is having fast changes in temperature like you're having ("snapping back"), it's often due to an air pocket. This can be caused by an air pocket in the coolant system, or combustion gases entering into the coolant (as in a bad head gasket).
To purge the coolant system, first make sure the coolant level is topped off and the reservoir is filled to the "MAX" line. Have the radiator cap installed. Raise the front of the vehicle as much as you can safely; you can jack it up and put it on jack stands, raise the front with a vehicle hoist or lift, drive the front wheels onto some car ramps or even park with the nose of the vehicle uphill. Start the engine and turn the heater on with it set to the hottest setting. Run the engine at 2000-3000 RPM for at least 10-minutes, or longer, if needed, making sure hot air is coming out of the heater vents (about 60 degrees C.). At that point, shut the lower the vehicle and shut the engine off. Top off the reservoir, if necessary. This should work as far as purging the air out. Re-check the coolant level, again, when the engine is cold and top off as necessary.
One other note: If it runs hot at idle but not when driving at highway speeds, you probably have a bad fan clutch.
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Discussion Starter #3
Thanks for the reply. So I did the sensor because that is the one the Haynes manual explains how to replace (not super easy as it was near the firewall requiring removal of the upper and lower plenum).

What is the location of the coolant temp sender?

I hope it's not the water control valve. That looks like quite an ordeal to get at, but that is next on the list.

Haynes also says "if an overheating indication occurs even when the engine is cold, check the wiring between the dash and sending unit for a short circuit to ground" I've done the sensor so I imagine it wants me to check the connection in the dash. Can you confirm this is something to check and I should take out the instrument cluster to do this?

Also, I have bled the system several times and I just dont think that it is as simple as air in the system unless the air is super hard to get out.
 

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Sup Mod keeping the peace
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Thanks for the reply. So I did the sensor because that is the one the Haynes manual explains how to replace (not super easy as it was near the firewall requiring removal of the upper and lower plenum).

What is the location of the coolant temp sender?

I hope it's not the water control valve. That looks like quite an ordeal to get at, but that is next on the list.

Haynes also says "if an overheating indication occurs even when the engine is cold, check the wiring between the dash and sending unit for a short circuit to ground" I've done the sensor so I imagine it wants me to check the connection in the dash. Can you confirm this is something to check and I should take out the instrument cluster to do this?

Also, I have bled the system several times and I just dont think that it is as simple as air in the system unless the air is super hard to get out.
Both the coolant temp sender and the coolant temp sensor are next to each other and next to the water control valve. They are all in the back of the engine.
 

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Sup Mod keeping the peace
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This will be fine ?


Sent from my iPhone using Tapatalk
According to this Nissan TSB: NTB09-040a - NEW BLUE NISSAN LONG LIFE ANTIFREEZE/COOLANT

SERVICE INFORMATION:
In calendar year 2009, Nissan began filling some vehicles at the factory with a NEW Nissan Long Life Antifreeze/Coolant (LLC) that is blue in color.
NOTE: LLC = Long Life Antifreeze/Coolant

Additional Information for using Blue LLC:

Blue LLC and Green-colored Nissan LLC (P/N 999MP-AF000P) are compatible with each other:
• Blue can be mixed/added with Green
• Green can be mixed/added with Blue

CAUTION:
• Adding Green LLC to Blue LLC will reduce/shorten the life expectancy of the Blue LLC to that of the Green LLC (4 years / 60,000 miles).
• LLC must always be used with demineralized or distilled water, otherwise the life expectancy of the LLC (Blue or Green) will be degraded and cooling system damage may occur.
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I would venture to say that you should be OK with the Blue. It's best to totally drain the coolant system of any Green coolant.
 

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NF Mod/Nissan Master Tech
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Yes, the Nissan Blue coolant is the right stuff. It is made by Pentosin and is the same as Pentosin Pentafrost A3 coolant. Xerex also makes a blue coolant for Asian cars and that will work, as well.
 

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According to this Nissan TSB: NTB09-040a - NEW BLUE NISSAN LONG LIFE ANTIFREEZE/COOLANT

SERVICE INFORMATION:
In calendar year 2009, Nissan began filling some vehicles at the factory with a NEW Nissan Long Life Antifreeze/Coolant (LLC) that is blue in color.
NOTE: LLC = Long Life Antifreeze/Coolant

Additional Information for using Blue LLC:

Blue LLC and Green-colored Nissan LLC (P/N 999MP-AF000P) are compatible with each other:
• Blue can be mixed/added with Green
• Green can be mixed/added with Blue

CAUTION:
• Adding Green LLC to Blue LLC will reduce/shorten the life expectancy of the Blue LLC to that of the Green LLC (4 years / 60,000 miles).
• LLC must always be used with demineralized or distilled water, otherwise the life expectancy of the LLC (Blue or Green) will be degraded and cooling system damage may occur.
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I would venture to say that you should be OK with the Blue. It's best to totally drain the coolant system of any Green coolant.
Can I Topup because soon it will reaching to minimum level or I have to drain it all ?


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Sup Mod keeping the peace
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Sure, you can just top it up. However to really take advantage of the improved longevity of the BLUE, it's best to drain the old stuff out and replace it with BLUE.
 
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