Car runs warm at idle

[Tom]

My car has started to heat up some at idle or stop and go traffic. One might think the fans aren’t coming on, but I checked and both fans come one and I can feel the air flow behind the radiator. Both fans seem to work.

My car is a 2002 Chevy Impala LS with the 3.8 l engine. The engine was rebuilt last summer and a new water pump was installed as part of the rebuild. The thermostat was also replaced at that time, and a lot of the hoses as well. The radiator was replaced a few months ago. The car is not losing coolant. I tried to bleed air from the sir valve on top of the thermostat housing, though I couldn’t detect any air coming out so I think there isn’t air in the system. The car holds a steady normal temp when driving.

Now the car is not OVER-heating. It doesn’t get TOO hot. My guage doesn’t show the actual temp but I think it normally runs 180-190 based on the notches on the dial. When sitting at idle, it moves up a couple more notches to what I suspect is 200-210. This is not really dangerous, but the car is 12 years old and for 11 years it never did this.

If anyone has an explanation or a fix for this, I would appreciate it.

Topic

[dan]

for the 3800 this should be normal operational temperature, the gauge should read the half way point which should be bout 200 degrees, at idle with the car sitting the cooling fans do not kick on until coolant temperature reaches roughly 220 degrees, most engine operational temperature is about 190-220 degrees, or the temp gauge will go up and down between 190 and 220 as the fans kick on and off…

with the car moving forward the thermostat simply regulates temperatures, as air flow constantly moves through the radiator with forward movement of the car…. engine temps should bounce up and down between 190-195 in my experiences the temp gauge usually sets just below half point at all times… and at idle sitting still once again will bounce between a little over half, and a little under half, if it starts heading too 3/4 mark then start too be concerned about over heating…

[dan]

this diagram i sort of scribbled up is best i can describe the temp gauge on most GM cars, half way point is about 200 degrees and the red line i have drawn in there is where it will bounce between 190-220 degrees, the thermostat in your car opens at 190 and the fans kick in at i believe 220

[URL=http://s49.photobucket.com/user/13aceofspades13/media/tempgauge.jpg.html][IMG]http://i49.photobucket.com/albums/f261/13aceofspades13/tempgauge.jpg[/IMG][/URL]

at the blue engine still cold, and a bad thermostat will sometimes have the temp gauge staying there resulting in no heat on a cold day! the orange point is where you should actually start getting concerned, and if it starts getting into the red, SHUT THE CAR OFF!

hope this helps!

[college man]

Your vehicle has a 195f thermostat. at idle you may come up a little.
It could be the thermostat brand you used. The tolerance may be different
than the OE. The best thing to do is plug a scanner in and read live data
and watch the coolant temp and when the fans come on.

http://www.ericthecarguy.com/faq/what-to-do-when-your-engine-overheats

[Tom]

Thanks for taking the time for the reply. I know my car isn’t dangerously hot, but where you drew the needle at the half way mark is where it gets now when I idle, or maybe just a bit higher than the middle mark. Not dangerous, but for 11 years and over a hundred thousand miles, the needle never got that high. So I am just puzzled, is all.

[Tom]

Good tip. I do have a scanner that can read live data.

[Bill]

The cooling fans on those cars don’t come on until 220 to 230f so the gauge will read higher in stop and go traffic than driving along at a steady speed. I wouldn’t be alarmed unless the gauge keeps climbing and does not drop when you start moving again.

[Lorrin Barth]

I know that on Ford Mustangs and on many of the newer Fords there can be grounding problems. This makes the temperature gauge read high. On my Mitsubishi, forget to connect the ground between the intake manifold and the firewall and the temperature gauge reads high.

The sender for the temperature gauge is a variable resistor that changes resistance with temperature. If there are grounding issues that is just more resistance in the circuit.

The reason I bring this up is because you had the engine rebuilt. It is far from unusual for one or more grounding wires to be overlooked and not connected when the engine is reinstalled. It happens all the time.

The solution in this case is to get a wiring diagram that shows the location of all underhood grounds. Then check if they are present.

[Neil Caulfield]

Now I see the importance of those, I left one of mine unhooked, should probably wire that back up! My gauge jumps around a little bit on my 93 Shadow, though it seems to also move consistently with how much cool air is passing throught he radiator

[dan]

it probably finally got that high because once again when you changed out the thermostat and the radiator and various other things in the cooling system it may have changed how everything operates just slightly, i have myself noticed a difference in temperature on my car after a thermostat removal, nothing dangerous just different.

[Author]

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