Fluctuating engine temperature

Tiny
FARHAN2149
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  • 2006 NISSAN MAXIMA
  • 3.0L
  • V6
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
My car temperature is sometimes fluctuate up and down on highway speed 100 km/h. I changed the thermostat before original it was okay, but after one month same problem appeared again. I changed the radiator cap and while touching the hose upper and lower they do not seems to be that hot. I measured it with gun showing 85c but gauge shows higher then 85c.
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Thursday, May 3rd, 2018 AT 4:29 AM

7 Replies

Tiny
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Is one or both of the cooling fans coming on and off while driving?
If so, did anyone hotwire or bypass any of the cooling fan/s wiring, etc?
85c is the same as 185F which is what I understand is not very hot. The thermostat is probably rated at just about that temperature.
Keep in mind though that the temperature sensor is located at a different location from where the hoses are and is usually screwed into the engine block or intake manifold or head where the engine coolant is located on the side of the thermostat that would be on the side before the thermostat opens.
If the engine temperature and coolant is not actually fluctuating then it might just be a loose electrical connection to/from the coolant temperature sensor or the gauge and/or a faulty temperature sensor or gauge. I would move your temperature gun to where the temperature sensor is and see if you can get a reading there and compare it to the gauge and if it is not the same or close start diagnosing if it is a faulty wire. So try wiggling the wires and see if the gauge fluctuates and if not try a new temperature sensor. Maybe even read the trouble codes and see if the computer has picked up a code for the voltage on that temperature sensor circuit.
Here is a test of the ect sensor on the kitchen stove boiling a pot of water.
The code for it is a P0117 or P0118.
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Thursday, May 3rd, 2018 AT 7:27 AM
Tiny
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Both of the cooling fans work properly. I did checked just the temperature of car is bouncing up in second and coming down in second even if the fan will not work. The car temperature will not bounce quickly straight 20c ahead of 82c thermostat and then bouncing down quickly. This car's thermostat is at lower hose. No cts at engine head there are two sensor on upper radiator hose. I think one is cts and other is cluster gauge sensor and in computer no fault found. The fan I checked at idle without A/C both fan runs automatically on right temperature and shut off at right temperature.
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Thursday, May 3rd, 2018 AT 11:30 AM
Tiny
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This sounds like an electrical problem between the coolant sensor and the gauge itself. Since it seems almost impossible for the gauge to bounce like that from the actual temperature of the coolant/engine changing that quickly. Check the electrical connections for a loose wire, etc.
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Thursday, May 3rd, 2018 AT 11:44 AM
Tiny
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Thanks for your reply. I will check the sensors, but I think more I have to ask three months before I have just changed the thermostat so is it possible if the thermostat is fault then temperature with bounce up and down this way?
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Thursday, May 3rd, 2018 AT 12:30 PM
Tiny
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If the gauge is actually bouncing or changing temperature more than just a few degrees within a few seconds. For instance changing from 180F to 165F and back to 190F and so forth in a matter of just a couple seconds and actually appears that the gauge is bouncing, it is impossible for the coolant to change temperature that quickly even if the thermostat was sticking. If it bounces that quickly in my mind it is an electrical problem. I would assume you could just hook a voltmeter up as close to the sensor itself as possible and monitor the voltage there and see if indeed the voltage bounces or not. Or try wiggling the wires while the engine is idling and warm and see if the gauge itself moves when wiggling the wires. Or better yet, wiggle them with the engine off, key on run, that way you know the coolant temperature cannot be changing.
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Thursday, May 3rd, 2018 AT 1:02 PM
Tiny
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Hi, I did noticed something else today while knocking on cluster temperature gauge and rpm bounce down to actual position and then going up. Now what this means I should change the whole cluster or it is repairable?
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Friday, May 4th, 2018 AT 11:29 AM
Tiny
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That sounds like maybe a loose ground to the cluster.
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Friday, May 4th, 2018 AT 11:34 AM

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