Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

Why does my "Low Coolant" light come on periodically?

Bought a used 2000 Pontiac Grand Am GT1 from someone a month or two ago. Ran fine for a while. Service engine light is on for evap small leak (think that’s unrelated to the coolant light?) anyways, recently the coolant light has come on for less than 60 seconds and then went off. (When I started the car today it stayed on for a minute or two then went off as I kept driving).

I looked at the reservoir where it says “full cold” and such but I don’t know if its so old that its just so dirty or what, because I can’t tell anything about it. Or maybe I don’t know what to look for.

Keep in mind the car did sit for about a year before I bought it…

Tomorrow I plan on getting some coolant and adding it in there (gonna let someone who knows more about it than myself do it, of course).

What could the problem be? Why is the low coolant light only coming on for short periods of time? (usually only once each time I drive it recently, sometimes not at all). Thanks

Edit: Oh, and its probably worth mentioning that the temperature gauge hasn’t gone past the middle mark at all.

148xxx miles.

Remove the cap from the reservoir, and see if the coolant looks like this.

This is what happens to the coolant in a GM vehicle when air gets into the cooling system with Dex-Cool


Bllllechhhhhhhh! Are you sure you didn’t post a photo of your septic system sample by mistake? Is my opinion of Dexcool showing?

Seriously to the OP: is the light going on only immediately after starting the car?
Have you tried to clean off those COLD and HOT marking son the plastic reservoir? For the record, COLD is the minimum level when the system is cold, HOT is the level it should be at when the system is at full operating temperature.

By all means check your coolant’s color as Tester recommended. It’s important.
But also visit that pro you mentioned. Ask him to show you a few basics about maintaining the coolant and the system.

Post his response. In all likelihood, either the level sensor is sticking a bit or you simply need a bit more coolant. The latter is more likely. Unless, of course, the coolant looks like Testers photo… yeeechhhhhh…
If it does you’ll need at least a system flush and fresh coolant.

Alright, I’ll check it out. That looks gross. I’ll post a response once I look at it.

Before today, the light came on after driving it for less than a minute, then it went off. One time it came on in the middle of my route then went off again. Today, it came on as soon as I cranked the car, then went off. It’s pretty random as to when the light comes on and you hear the chime.

Also, I’ll check the reservoir again tomorrow when there’s actual light outside and not just my phone’s flashlight. Thanks for the reply!

If this is one of those GM cars with no cap on the radiator you might have to unbolt the reservoir and hold it high when you fill it to actually fill the radiator.

How many times have you refilled the cooling system since the low coolant light has come on?

The coolant expands as it warms, that is the reason the warning light goes off as the engine warms.

My son has a 2000 Grand Am GT. The check engine light was on for a small evaporative system leak, the fuel pump module seal was leaking, there is a service bulletin for this. I think the seal was $10-15.

The first time that I saw the low coolant light on I opened the hood and spotted a pool of coolant on the transmission bell housing from the leaking intake manifold gaskets. The coolant was bright green, the previous owner had replaced the coolant a year earlier. The color of the coolant does not indicate if there is a leak.

I haven’t yet changed the coolant at all. Heck, I don’t even know if the previous owner did. I plan to get someone to add coolant today to it.

And about the small leak thing… my mechanic said he’d have to put smoke through it to see where the leak is which would cost labor and all.

Has he even looked? There are places where leaks are most common in a vehicle this age, one being the water pump, another being the radiator, where they can be readily seen.

Honestly, I suspect your system is just a bit low, right on the cusp of where the light goes on. Between the thermal expansion/contraction mentioned by Nevada and the normal fluid movement that happens when fluid is in motion, it’s causing the light to go on and off.

Try adding a bit of coolant and see if the symptom disappears. Post the results.

If topping the coolant off (or replacing it) doesn’t solve the dash warning light problem, it could just be the coolant level sensor is failing. I seem to recall that has been a complaint here before.