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So I have a 2011 Xterra, 150,000 miles. It has been the best vehicle for the last five year but all of a sudden my temperature gauge started rising until it reached that notch before over heating. I have changed the thermostat, temperature gauge, heater core hose, heater core hose assembly, the tensioner, serpentine belt, water pump, timing belt tensioner, and finally the radiator. I have essentially put an entirely new coolant system in the car and it is still having the same problem! The temperature rises after reaching 60 mph and over, then it continues to fluctuate the entire drive. If anyone has any more ideas they would be much appreciated.
 

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what thermostat did you put in? can you provide part number and brand? and how is the radiator cap and condtion of coolant in the reserve? any other symptoms? any loss of power as this occurs? does the gauge rise sitting at a light in traffic?
 

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Thanks for your response! I bought a CarQuest full thermostat (with the housing.) The radiator cap is my next purchase. I have done multiple pressure tests and it is holding the 15.2 psi for over an hour. It does fluctuate at stop lights or when I park and wait. No loss of power, and all the other gauges seems to work fine. I hope this helps!
 

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Pretty common symptoms of head gasket failure.

But it could also be the fan clutch. If it runs cool sitting still and idling for a long time, but heats up on the highway, the fan clutch has failed.
 

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I disagree with this. Overheating at speed is almost always an airflow restriction or circulation issue. The fan does little to nothing at highway speed and it’s function wouldn’t affect your temperature. Also, the most common failure of the OE clutch is that it stays on and fuel economy suffers. People usually describe their truck “sounding like an airplane” or similar. Head gaskets in themselves don’t really cause overheating, it’s the constant loss of coolant that results in higher temperatures. The very first thing I would check is correct cap installation. People often put the spring loaded cap on the radiator instead of on the degassing tank and the cooling system won’t purge air as a result. Seen many overheat this way.
 

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I disagree with this. Overheating at speed is almost always an airflow restriction or circulation issue. The fan does little to nothing at highway speed and it’s function wouldn’t affect your temperature. Also, the most common failure of the OE clutch is that it stays on and fuel economy suffers. People usually describe their truck “sounding like an airplane” or similar. Head gaskets in themselves don’t really cause overheating, it’s the constant loss of coolant that results in higher temperatures. The very first thing I would check is correct cap installation. People often put the spring loaded cap on the radiator instead of on the degassing tank and the cooling system won’t purge air as a result. Seen many overheat this way.
that was going to be almost my exact reply.
 

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Thanks for your response! I bought a CarQuest full thermostat (with the housing.) The radiator cap is my next purchase. I have done multiple pressure tests and it is holding the 15.2 psi for over an hour. It does fluctuate at stop lights or when I park and wait. No loss of power, and all the other gauges seems to work fine. I hope this helps!
whats the temp rating on that thermostat you bought, and when you did this did you dio a cooling system burping to ensure it has no air pockets?
 

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So I’ve burped it manually multiple times. I’ll have to check the temperature rating on the thermostat I bought. So i did an emissions test to see if it was the head gasket and that came back negative. The a/c and heat work fine. However when the temperature gets too high the a/c will start running warmer. I noticed that the a/c pulley is only spinning when the a/c is on so I’m thinking their is a bearing messed up in there. The temperature gauge will rise to just under the notch then continue to fluctuate. I’ve been sitting in the driveway for about 5 minutes and it’s back to normal.
 

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the center of the Ac pulley is part of the ac clutch and will only spin when engaged. This is used in place of a variable displacement compressor to avoid over pressure

I only use OE thermostats. Others here have had overheating issues with aftermarket ones. Also, I’d verify proper cap installation.
 

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the center of the Ac pulley is part of the ac clutch and will only spin when engaged. This is used in place of a variable displacement compressor to avoid over pressure

I only use OE thermostats. Others here have had overheating issues with aftermarket ones. Also, I’d verify proper cap installation.
do as he said, check cap, also check that the jiggle valve is not stuck on the new thermostat and that you didnt maybe accidentally kink a hose slightly causing flow restrictions and i am in agreeance many aftermalet thermostats will have the correct rated temp but not actually work as well as the oem versions.
 

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I had the same problems, just a different vehicle. Turned out to be two culprits, leaking head gasket and clogged catalytic converter. Stripped out the converter(not legal in a lot of states)got the car running fine until the head gasket blew and the car died.
 

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I had the same problems, just a different vehicle. Turned out to be two culprits, leaking head gasket and clogged catalytic converter. Stripped out the converter(not legal in a lot of states)got the car running fine until the head gasket blew and the car died.
"not legal" aka find your town's little mexico and have it "inspected"
 

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A good way to know if your head gasket is bad is the coolant reservoir...

if the radiator doesn't draw the coolant back out of the reservoir, it's usually a bad head gasket. I went through almost exactly what you are on a vg30dett. It would sit and idle and maintain perfect temps. As soon as I got the motor under load, the temp would start going up. I flushed the cooling system, new hoses, new coolant reservoir hose, and radiator cap. Nothing made any difference until I changed the head gaskets. cylinder four was leaking combustion into the cooling system.
 

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This wouldn’t apply to their xterra because these two models have different type of reservoirs. The vg30 has an expansion tank and the vq40 has a degassing tank. These types of tanks have two hoses, one is an inlet and the other is an outlet. The tank on these vehicles is part of the cooling circuit and the radiator will never “draw the coolant back out” This is why the radiator has a flat cap with no spring and the degassing tank has a cap with a spring like traditional radiators.
 
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