"Low Coolant" light doesn't vanish.

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I started getting a "low coolant" light lately. It disappears after a bit of driving.

I was worried I had a leak of sorts, so I checked the level. It was fine. If not, too high.

The obvious next step was that there was air in the system, so I opened the dribbler valve right above the thermostat while the engine was hot, and closed it afterwards.

The light still pops up every time.

Could this be because my thermostat doesn't have a hole in it?
 
Open the cap with the engine cold and see if it needs any, this is common with these. Don't go by the level in the overflow bottle.
 
My brother had a 1999 Buick Century that my grandfather owned before him. It had the low coolant light on for years. Never did figure it out, but didn't care because the level was fine.
 
My 1999 5.7L was giving me this problem about 3 years ago, a common occurrence on these cars as they age. No doubt the sensor had never been cleaned. While it wasn't gunked up in the last, a light cleaning of the metal probe with fine sandpaper cleared it up. No problems since.
 
Originally Posted By: Nick1994
My brother had a 1999 Buick Century that my grandfather owned before him. It had the low coolant light on for years. Never did figure it out, but didn't care because the level was fine.


On these cars if the radiator ever needs changing you need to drill a hole for the sensor on many replacement radiators to get fluid or the sensor will stay dry and the light on.
Even a new OE Delco needs drilling, the boss is there and you can put a sensor in but its a dry hole until you drill through.
The reason for this is the radiator also fits cars with the sensor in the overflow bottle.
 
It turns out, coolant wasn't draining from the reservoir properly. Pulled the hose out, and nothing came through.

So I replaced the hose, and it seems to work. It still pops up sometimes, but disappears when the engine warms up. Does that sound like it needs to be burped again?
 
My Pontiac does that too sometines, as mentioned take the coolant level sensor out and either replace with a new one or just try cleaning off the crude on the end of the sensor and reinstall, that HAS worked for me in the past too. YMMV
 
Originally Posted By: OpenClose
OK, so it still pops up, but it always disappears when the car warms up. What could cause this?


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The sender everyone mentioned in this same thread?
 
Well yeah. I just figured an actual BAD sender would just result in the Low Coolant light being on all the time.

The fact that it disappears after a bit makes me think it is dirty, or maybe there is still a coolant bubble in there that goes away when the thermostat opens. After all, I didn't drill my thermostat before I put it in, and apparently that is recommended.
 
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