Cooling System Issues

Tiny
NFA305
  • MEMBER
  • 2006 CHEVROLET IMPALA
  • 54,000 MILES
When I do city driving for more than an hour, I notice the temperature gauge reads slighty higher than usual. I recently had an overheating issue which seemed to be caused by a faulty O ring in the Radiator Top. Dex cool was added and everything was fine now it seems the car gradually gets hotter. Please help! Am about to go to dealer and pay 105.00 so they can tell me wtf is wrong!

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Thursday, October 13th, 2011 AT 7:05 PM

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Tiny
CARADIODOC
  • EXPERT
"Slightly higher than usual" is not a problem and it is to be expected at slower speeds when there isn't the natural air flow through the radiator. A lot of GM cars don't turn the electric radiator fan on until the coolant temperature gets up to 220 degrees which is not considered abnormal. At highway speeds it will run closer to 195 degrees.

If you want to do anything, the next time it's scheduled for a cooling system flush, get the "Dex-Mud" out of there and put in regular antifreeze.
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Thursday, October 13th, 2011 AT 7:17 PM
Tiny
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The thing is that when I drive it int he city for about an hr and then turn it off. When I turn it back on the temp gauge is on the next line past the middle. As I drive It comes back to its regular temperature. This hasnt ever happen before
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Thursday, October 13th, 2011 AT 7:37 PM
Tiny
CARADIODOC
  • EXPERT
The heat is produced in the engine in an area away from the temperature sensor. When you turn the engine off, that heat migrates around and there is no cool coolant coming in from the radiator until the engine is restarted. That higher temperature shows up on the gauge when you restart the hot engine, then it goes down quickly when the cool coolant comes in from the radiator. You can prove that to yourself by turning the ignition switch back on right after stopping the engine. The temperature gauge will go up over a period of about five minutes. You know the engine temperature isn't really going up because it isn't running. The heat from deep inside the engine is finding its way to the temperature sensor.

You're more observant than most drivers, but I think you don't actually have a problem that is of concern. Five years after replacing the thermostat on my '88 Grand Caravan, the temperature gauge started going into the "red" zone after driving five miles, then it would suddenly drop to cold, go back up, then down a few times until it settled out. All it needed was to have a tiny bypass hole drilled into into it like the original one had. The real question was, why didn't it act up for the first five years? Something changed in the system. That's not to say something was defective. It just means something was different.

All summer long my temperature gauge has been hanging around half scale. Today it's down to the low 50s outside and my gauge is suddenly staying below 1/4 scale. The heater will still burn me out but the cooling system is fine. The best I can suggest is it's common for temperature gauges to read slightly differently under different conditions, (outside temperature, road speed, AC on or off, pulling a trailer, etc.), But from what you've observed, I don't think you have a problem.

One other thing you might consider is you mentioned adding some coolant. If you did not add 50 percent water with it, the ratio of antifreeze to water changed. Antifreeze does not hold as many BTUs as water. That means your coolant mixture now will rise in temperature faster as the engine warms up and it will transfer that heat to the radiator at a slower rate. In response, the thermostat will just open up sooner and stay open further, longer, so the temperature remains correct. That can easily explain the change you're seeing in the temperature gauge. Again, nothing to worry about, but keep watching it.
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Thursday, October 13th, 2011 AT 8:24 PM
Tiny
NFA305
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I am considering doing a coolant system flush.I have a feeling my radiator needs a flush.
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Thursday, October 13th, 2011 AT 8:53 PM

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