Low coolant light

Tiny
JR47
  • MEMBER
  • 1999 PONTIAC GRAND PRIX
  • 3.8L
  • V6
  • FWD
  • AUTOMATIC
  • 205,713 MILES
For the past week my low coolant light has been turning on and off and I have checked the coolant level several times both hot and cold levels and it was right on where it needs to be but there was only one time when I actually needed to add coolant but I only had to add a small amount of it. If you need to know the time when it needed coolant was for the hot level indicator. Any idea on what's going on here?
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Saturday, June 20th, 2015 AT 12:28 AM

19 Replies

Tiny
WRENCHER1
  • MEMBER
Ho Doc

The coolant level sensor in this car is not a float and it's not in the reservoir. It's a liquid sensor that is in the radiator so the first thing to do is verify the coolant level in the radiator, not just the reservoir. This type of sensor does fail quite often so that could be your problem also. It snaps into the radiator.

https://www.2carpros.com/images/external/78447601.jpg.gif
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Saturday, June 20th, 2015 AT 5:33 AM
Tiny
WRENCHER1
  • MEMBER
That was supposed to be Hi not Ho Doc. LOL
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Saturday, June 20th, 2015 AT 5:34 AM
Tiny
CARADIODOC
  • EXPERT
Dandy. Thank you for setting me straight. I've never run into this one before.

You're truly a wonderful human being!
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Saturday, June 20th, 2015 AT 9:36 PM
Tiny
WRENCHER1
  • MEMBER
It's a 3 wire sensor that shares the same reference voltage as most other sensors and I've had them get shorted and cause some real driveability problems by pulling down the reference voltage for some vital sensors.
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Sunday, June 21st, 2015 AT 3:47 AM
Tiny
JR47
  • MEMBER
Ok guys the light went on and off again yesterday and I did check both levels in the radiator and the reservoir and both were full. But one thing I found is that there is some type of sludge build up on the inside of the filler neck of the radiator and under the radiator cap itself. I have a photo of it and ill try to upload it. If the photo didnt upload the sludge stuff is a very light brown almost tanish in color, plus its not really thick its actualy a thin layer of it.
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Wednesday, June 24th, 2015 AT 1:02 PM
Tiny
CARADIODOC
  • EXPERT
I doubt that's the issue. Look for the sensor that Wrenchtech mentioned.
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Thursday, June 25th, 2015 AT 12:55 AM
Tiny
WRENCHER1
  • MEMBER
It is possible that the sludge or whatever that stuff is s coated the sensor probes, making it deliver faulty readings. You need to find out what that stuff is. It could be leaking trans fluid due to a bad cooler in the radiator.
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Thursday, June 25th, 2015 AT 1:59 AM
Tiny
SPROCKIE
  • MEMBER
  • 1999 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 157,000 MILES
My add coolant light came on. I checked the oil. It doesn't look like it is leaking into it with a head gasket gone. The coolant is coming up out of the resovoir tank.
I can see it on the side of the top and down below. Is this the thermostat? Or something else?

Thanks
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Wednesday, October 30th, 2019 AT 5:59 PM (Merged)
Tiny
MMPRINCE4000
  • EXPERT
If the coolant tank is overflowing and there are air bubbles in it, have a compression test performed on the engine, see if it is a headgasket problem.

If compression is OK, then look to thermostat, radiator cap, or waterpump.
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Wednesday, October 30th, 2019 AT 5:59 PM (Merged)
Tiny
DANCRAD
  • MEMBER
  • 1998 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 126,000 MILES
Approx 2 months ago I had 2 fill my coolant, light came on checked and was low. After about a month coolant light continued to come on and off checked again periodically seemed to be ok. This week had to fill again, light still came on after filling. Now ive noticed my temp gauge is running high. Not sure what problem is not finding coolant on ground even if car is parked for 3-4 days? Also when temp gauge running high it jumps up and down alot? HELP!
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Wednesday, October 30th, 2019 AT 5:59 PM (Merged)
Tiny
RICH8425
  • MEMBER
I too had this light come on as well with no leaks on the ground. Found out it was leaking on the engine and really had to go in and look to find coolant leaking from some heater bypass pipe located right above the water pump. BUt not sure if this is the same scenario you have. It could be leaking coolant into the engine (like a head gasket leak) so check your oil. If you see any foam that could be it. There's no steam coming out of your tail pipe right? Also go around the engine and try and see if you can smell coolant. Has a distinct smell and may help you find the leak.
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Wednesday, October 30th, 2019 AT 5:59 PM (Merged)
Tiny
SHIFTRACING
  • MEMBER
  • 1997 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 10,500 MILES
I drained my radiator and replaced my thermostat on my '97 pontiac grand prix 3.8 SE. I then got help from a teacher at school, porter and chester institute, on how to go about refilling the radiator. He helped me fill it up to the specifications. It ran well in the shop but when I drove it home, which is thirty miles away, my low coolant light came on and when I came to a stop, it turned off. I drove it for another 5 mins and it didn't come back on but during the whole time I was driving, the tempature gauge rose up a little but didn't reach the middle of the gauge like it's supposed to. It's the weekend and I need some help, any answers?
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Wednesday, October 30th, 2019 AT 5:59 PM (Merged)
Tiny
MERLIN2021
  • EXPERT
Look at the recovery tank, is the coolant level OK? You may have had an air pocket, and when the car cools off, open the tank, if level is OK and no leaks are found, you are probably good. If leaks are found fix leaks!
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Wednesday, October 30th, 2019 AT 5:59 PM (Merged)
Tiny
NPARHAM8
  • MEMBER
  • 1994 PONTIAC GRAND PRIX
  • 6 CYL
  • AWD
  • AUTOMATIC
  • 186,012 MILES
Hello. I am posting today because my 1994 pontiac grand prix is acting wierd. Well, to keep it pretty cut and dry: the car tends to cut off while driving AND while idling. I can start the car ok, drive up the block, maybe about 10-15 blocks on average, before it starts acting all goofy on me. I had the car looked at by two different Unofficial mechanics and they both(unknowning of one another) said the same thing: the engine was being choked out. They replaced the vaccum line and pcv value(i think), I think it was, its the hose that goes over the engine and also has a "plug" that goes into the engine to keep from alot of air getting into the engine. That unfortuneatley did not help. The second guy used a silicone gasket maker around the "plug" of that line that was replace, but that did not help. If more info is needed, please ask. I also can take photos if needed.
Ps. I also dont have trouble starting the car. I only have problems starting the car AFTER it has already cut off on me, which made me to believe it was not the starter. I had the battery tested as well and accoring to advance auto parts, the battery is fairly good. It has 650 cca /711 cca or something like that. Im not too hip to the car lingo. I was also told the alternator was fine and had my oil changed recently. Also, the low coolant light tends to be on but the antifreeze is filled. Actually, it is filled above the hot fill, but I was having my problems prior. The service engine light tends to come on too, but not as often as the low coolant.
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Wednesday, October 30th, 2019 AT 6:00 PM (Merged)
Tiny
JACK42
  • EXPERT
The service engine light may be the key to finding out what is wrong with the car, that is the computers way of telling you it sees a failure in the system, which can cause stalling or a no-start condition. When it dies adn wont start, you need to check for fuel pressure adn spark. At the mileage you are at it could be a number of things, so we need to see what is missing that is keeping it from starting
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Wednesday, October 30th, 2019 AT 6:00 PM (Merged)
Tiny
NPARHAM8
  • MEMBER
Ahh. I hear what your saying. I also noticed something today that I may not have specified and I thought was kinda wierd: the low coolant light. The reason I say its wierd because it looks pretty fulll. Its at the "hot fill" line with the correct fluid, but, the car seems to shut off after about 10-15 minutes of driving as if it were overheating. And once it cuts off, the car does NOT even turnover/make a noise when trying to start it, I mean silent, as if there was not even a starter installed, silent. Just thought I had as much info as possible.

PS - the car neveeerrrrrrrr NEVER has a problem starting until AFTER it has shut off. After that, I have a problem starting it, but if I let it sit for 15-60 minutes, im ok and will enter the "on again, off again" loop again.
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Wednesday, October 30th, 2019 AT 6:00 PM (Merged)
Tiny
JACK42
  • EXPERT
Do you have other electrical in the car when it has shut down? ( Dash, radio, headlights?)
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Wednesday, October 30th, 2019 AT 6:00 PM (Merged)
Tiny
NPARHAM8
  • MEMBER
Yes. When it cuts off, I still have access to all those things, as if the battery was on before I turn the key any further to start the car.
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Wednesday, October 30th, 2019 AT 6:00 PM (Merged)
Tiny
JACK42
  • EXPERT
When it is hot and wont crank over, you need to test for power at the small wire on the starter using a test light. Also test for power at the injectors with a test light with the key on when it wont do anything. We need to see what has power if it wont crank after it dies but th edash works
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Wednesday, October 30th, 2019 AT 6:00 PM (Merged)

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