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Old 01-25-2016, 10:49 PM   #1
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Default Fluctuating Coolant Temp

I just now noticed in the winter, my car coolant temp sensor has been different. My car is not overheating but when I drive, the need fluctuates between 160-190. 2 lines above 160 and 2 lines below 190, it would move up and down. When idling, gauge goes to 190ish and stays there, any advice?
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Old 01-26-2016, 12:22 AM   #2
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Coolant temperature variations are completely normal. When cruising, the thermostat will be regulating the minimum temperature of the engine (185-190* on a 195* stock thermostat), then when you come to a stop, the temperature will start to climb because of no air flowing through the radiator, until the fan set point comes on (215-225 depending on application) at which point the fans should maintain maximum idle temperature. If the engine is lingering outside of this window, than something is likely not right.

Also keep in mind that GM is notorious for inaccurate gauges and stepper motor failures in clusters. Later models have even been known to pin the gauge at a specific temp when within the normal operating range, just to remove any confusion from the normal range.

In my '94 Regal, normal operating range accounts for 25% of the gauge. The remaining is either warmup, or beyond normal range, which if it'* up there, there should be a reason for it.
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Old 01-26-2016, 12:25 AM   #3
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Okay thank you. Seems like it got worst in the winter, like it goes down and up below the 190F mark when I drive, didn't seem to do this in the summer though. I agree on GM gauges though, the gas gauge goes up 1-2 lines when i turn off the car

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Coolant temperature variations are completely normal. When cruising, the thermostat will be regulating the minimum temperature of the engine (185-190* on a 195* stock thermostat), then when you come to a stop, the temperature will start to climb because of no air flowing through the radiator, until the fan set point comes on (215-225 depending on application) at which point the fans should maintain maximum idle temperature. If the engine is lingering outside of this window, than something is likely not right.

Also keep in mind that GM is notorious for inaccurate gauges and stepper motor failures in clusters. Later models have even been known to pin the gauge at a specific temp when within the normal operating range, just to remove any confusion from the normal range.

In my '94 Regal, normal operating range accounts for 25% of the gauge. The remaining is either warmup, or beyond normal range, which if it'* up there, there should be a reason for it.
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Old 01-26-2016, 12:27 AM   #4
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To clarify, its possible you may be dropping below normal range at cruise, which could be causing the gauge to drop out of 'normal operating range'. I am not sure where you live, you may be due for a replacement thermostat, you are not using a stock temperature unit, or it is so cold the car can't retain heat.

What part of the country do you live in, and what temperatures/weather are you dealing with?
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Old 01-26-2016, 12:30 AM   #5
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What you mean i am not using a stock temp unit? I live in GA , right now it gets 30F-60F. Couple days ago its been 26-35F. When I idle, gauge sits perfectly fine at 190, 191F.

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To clarify, its possible you may be dropping below normal range at cruise, which could be causing the gauge to drop out of 'normal operating range'. I am not sure where you live, you may be due for a replacement thermostat, you are not using a stock temperature unit, or it is so cold the car can't retain heat.

What part of the country do you live in, and what temperatures/weather are you dealing with?
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Old 01-26-2016, 12:31 AM   #6
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When it goes up and down, it goes 2 lines below 190 and 2 lines above 160F, it fluctuates but my car does not overheat. Should I worry? I just spent $250 fixing my AC
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Old 01-26-2016, 03:02 PM   #7
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i am going to try and replace my thermostat today, so does my coolant temp sensor seem fine? Read mixed reviews of the sensor and the thermostat
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Originally Posted by rjolly87 View Post
To clarify, its possible you may be dropping below normal range at cruise, which could be causing the gauge to drop out of 'normal operating range'. I am not sure where you live, you may be due for a replacement thermostat, you are not using a stock temperature unit, or it is so cold the car can't retain heat.

What part of the country do you live in, and what temperatures/weather are you dealing with?
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Old 01-26-2016, 10:12 PM   #8
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Without knowing what the actual temperature is, I wouldn't know if it'* the thermostat, temp sensor, or even gauge to blame.

In all honesty, even this morning, I was driving the Regal and noticed mine getting too cool for a bit while moving after setting idle for a spell, it took a minute for the thermostat to close back up and push the temperature up a bit. You may be noticing normal behavior, or even a part starting to show its age.
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Old 01-26-2016, 10:20 PM   #9
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I bought the thermostat, any tips u suggest before I install?
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Without knowing what the actual temperature is, I wouldn't know if it'* the thermostat, temp sensor, or even gauge to blame.

In all honesty, even this morning, I was driving the Regal and noticed mine getting too cool for a bit while moving after setting idle for a spell, it took a minute for the thermostat to close back up and push the temperature up a bit. You may be noticing normal behavior, or even a part starting to show its age.
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Old 01-26-2016, 10:25 PM   #10
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Did you get the Delco 195 degree?
I had the Park Ave out in sub freezing temps, and I was surprised that even with a new Delco 195 thermostat, the car cruised at around 180F or a bit less sometimes, when normally it would be around 192 in cooler temps.
Mainly that cool air coming though the rad, is chilly, and no need to worry about fans coming on, dang it was cold out.
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