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Car overheating or bad Temp Gauge?
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BDRTFM
New User
Dec 2, 2015, 8:11 AM
Post #1 of 8
(1606 views)
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Car overheating or bad Temp Gauge?
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I recently got an 02 Buick Century from a relative who is also a backyard mechanic. He was able to drive the car 100 miles or so without heating issues when he drove it out of town and back. However, when I turn the key, even before turning the engine over, early in the morning when the temp outside is pretty cool, the temp gauge immediately jumps to half way which indicates normal running temp - before I even start the car. Within minutes of starting the car, before I go more than a few blocks, the gauge is in the red and then the temp warning light comes on. I don't know if it's just my imagination but, it seems I can smell something as if the car is getting hot. But, like I said, that may be just because I am expecting to sense something that should be there if the car is overheating. So I parked the car and left it and told my relative about it. He came over, looked at the temp gauge needle without the car running, saw it climb a bit and said that there is either a short in the sending unit or a bad unit and he disconnected the gauge completely. I assumed there was something causing the car to overheat but, he said it looked like their was plenty of coolant when he checked it a week ago and that he didn't think there was a stuck thermostat so, it should be ok to drive for a few days without the temp being monitored.
I need to use the vehicle to get the kids to and from school and such but am afraid to drive it with no temp monitor at all. I still don't know if the car really is overheating or if it's an issue with the gauge. And it worries me that the fan won't kick in once the engine does start to get hot. So not sure if I should be driving the vehicle at all or what the actual problem could be. If anyone can give me an idea of what to do from here, it would be great.
Thanks.
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kev2
Veteran
Dec 2, 2015, 9:12 AM
Post #2 of 8
(1595 views)
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Re: Car overheating or bad Temp Gauge?
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step 1 get the system scanned- its free at most part stores. Especially if the light is off.
then post all codes, also tell us which engine... someone will advise.
check coolant level before driving...
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BDRTFM
New User
Dec 2, 2015, 10:08 AM
Post #3 of 8
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Re: Car overheating or bad Temp Gauge?
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I'll try to get it scanned and post them but, the nearest place that can do a scan is a bit of a drive so, guess I have to hope I don't get stranded half way there or back. I have to grab the kids at school and not sure I trust even doing that. Really don't want to end up blowing a head gasket or worse. Not sure why he disconnected the sensor? I'd rather have an off reading with the temp warning light and fan coming on prematurely than have no reading at all.
Thanks.
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 2, 2015, 10:32 AM
Post #4 of 8
(1587 views)
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Re: Car overheating or bad Temp Gauge?
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Arggh! Feel your frustration with no quick way to know if real or a problem that's real.
1. Do fans come on when reading is in or near the red zone?
1a. If not try this: Some even cold will force fans if not working properly to run with A/C or defrost request and would cool down even if you asked for the warmest request on the gauge if correct and no other issues.
2. A good clue with no tools it's overheating for real is if you know it's full of coolant - radiator included run heat full blast and feel air. If climate controlled that's not engine temp air but should be warm and pretty even for what you requested. If it goes cold it strongly suggests coolant is low or boiling as air thru a heater core doesn't transfer heated air well or much at all spells trouble is real.
3. If system can't hold pressure as felt (use a glove) at upper radiator hose you can feel it as it warms up from cold many vehicles do not cool or run fans over the boiling point of even the antifreeze mix so you are circulating air or bubbles - that's bad.
That can be just a pressure cap failed or a lot of reasons.
Some if cool ambient air and steadily moving along will be cool enough to be stable then rise when stopped or moving slowly like below 30-40ish MPH.
These just some things you can do to have some idea of real trouble or slight issue or find a problem with no tools, no codes nor accurate testing.
That only reduces odds if those things work not a fix nor assurance it can't really overheat.
There's a risk every time you drive that something will happen that strands you but can lower the odds.
Best you can do if you must drive it and hate to say stop if really overheating you'll be stranded anyway so don't make it worse,
T
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Discretesignals
Ultimate Carjunky
/ Moderator
Dec 2, 2015, 1:03 PM
Post #5 of 8
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Re: Car overheating or bad Temp Gauge?
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When they scan it, it will have a coolant temperature sensor code stored because the sensor is unplugged. If he unplugged the sensor and the gauge is at zero, it isn't a short in the wiring. Probably something wrong with the sensor or there is some resistance on the ground side of the coolant sensor circuit.
You need that sensor operational not only for the gauge, but the PCM for fueling and fan operation.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Dec 2, 2015, 1:05 PM)
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BDRTFM
New User
Dec 2, 2015, 1:16 PM
Post #6 of 8
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Re: Car overheating or bad Temp Gauge?
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Even with the sensor removed, the fan comes on almost immediately. As soon as I started the car when the sensor was plugged in, the needle immediately goes to the center even though the engine is cool an within 5 minutes or so, the fan comes on. And the heater is blowing warm air. I mean really warm air. I don't know if it's because my old cavalier didn't have a good heating system and just not used to it but the heat coming out of the vents in this car is very warm. I was feeling the line right where the thermostat goes into the engine and the line took quite awhile to get warm. It was pretty cool even after 15 minutes or so of idling. But it did eventually get warm. Not hot, just warm. And I haven't seen any coolant getting dumped into the reservoir either. But then, that's just while idling and revving the engine a bit in the driveway, not actually taking it for a ride. I'm tempted to just plug the sensor back in but, it won't really do much good because I still don't know if it's a bad sensor or something else like an air bubble or gelled up parts. I mean, until I see steam coming out of the cap or can fry an egg on the hood, I really can't tell if the warning light and needle going completely into the red are because of actual over heating or a bad sensor. I've never driven this car before so, I've no idea what is normal for it to make any judgement calls at all. I'll just have to risk driving to a place that can give me a code but, often those codes are pretty cryptic as well. Like my old cavalier that had a code saying their was a problem with holding a vacuum. That could have been any number of things. Turned out to be a almost invisible crack in the gas intake stem. But at least the code will give an idea where to start.
Thanks.
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BDRTFM
New User
Dec 2, 2015, 1:21 PM
Post #7 of 8
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Re: Car overheating or bad Temp Gauge?
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So maybe the sensor itself is somehow creating a ground or resistance and causing the gauge to pickup an higher reading than the actual temp? I know when he unplugged it, the needle dropped to zero. And when plugged in, it never goes below half way. I was starting to wonder if maybe the stepper motor in the cluster was going bad but am not sure if each motor runs more than one gauge. So should I plug the sensor back in before the scan or will the code still be in there anyway?
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Dec 2, 2015, 3:11 PM
Post #8 of 8
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Re: Car overheating or bad Temp Gauge?
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Tired at the moment - sorry. By unplugging this or things you are going to set codes no doubt that will remain for some time.
IDK - I find more troubles with connections and wiring for wrong info. In car you can test ohms thru the sensor at what exact temp known right where it's sensing. Some goofy to work with but infrared thermo pointed right at it should tell the actual temp and read on dash about that and sensor show the ohms thru it at given temps.
Plug it in and still get codes for some direction and check wires to it for anything wrong just because trying not to unplug stuff before a code reading,
T
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