Had a Low Coolant warning the other day. Looked at the reservoir and it was almost empty so I added coolant. I've only had this car for a short while and driven it a few hundred miles. The car is an 06 with 38,600 miles. I'm not sure why the level is low cause I can see no sign of it. I know there are issues with water pumps and fittings, plastic radiator and hoses. I'm going to drive it a bit and see if the level goes down again. If it does I'll have to take it somewhere and find out why. It's hard to find someone who is familiar with corvettes except a local dealer. As long as it is not the head gasket or engine related I can deal with it but if it's not I don't know what I will do.

 

To start off, there is no coolant sensor in the car to begin with. Hence system monitors how fast/slow the system takes to come up to temp, as well as if there is drastic change swing in engine temp, and if this happens, you get the Low coolant warning.

As for Dexcool level in the tank, if you look at the front of the tank on the head light side, you will see the full line at the top of the white part of the tank. So since the tank is angled, when looking at from the side, tank will look to be about half way emtpy on the back side, when the tank is filled to it full line at the front of the tank. Also, use only orange Dexcool mixed with water at 50/50, and if used anything (green antifreeze) to fill the tank, the entire system will need to be flushed including the heater coils as well. Hence the correct radiator fluid Dexcool, and green anti-freeze mixed together in the cooling system is going to cause a mess in system.

So back to the problem, and that your car has a wild temp swing in engine temp and this caused the warning.
Most of the time, the problem is air in the radiator system that causes this problem, and to purge the air, just need to put a vacuum on the take at the motor it running, which sucks the air out off the system that can get trapped when the fluid is changed.

But still have a set back on what you are calling the reserve tank empty. Hence was radiator fluid changed and system not purged of air to cause the tank to be low as it was trying to self burp reacently, or do you have a leak in the system that is causing the low fluid problem to introduce the air now isntead.

99% of the time when you have a leak in the system, it will be from the water pump, with water leaking out of the shaft. So with motor stopped, reach behind the bottom of the water pump pulley to feel inside it, to see if it wet. The other times, will be either something like the heat coil leaking (cabin will smell of raditor fluid), one of the raditor piping T's is cracked, or side plastic sides of the raditor is leaking isntead. Hence may be time to do a pressure test on the system, to make sure you don't have a leak in the system to start with, and what caused the Dexcool level in the tank to be low to begin with.

So if you are not smelling dexcool raditor fluid anywhere to suspect a leak, then would get a vacuum on the tank to begin with to burb any air out of the system for starters, and make sure that you have the tank filled to the fill fill mark with only 50/50 dexcool in the system. This way you can monitor the tank to just make sure it not leaking with no air in the system to start with

Next, the raditor temp sensor in in the front of the drivers side head on the front/side of the motor.


So on that note, would pull the fuel rail cover up enough to get at the sensor connector, disconnect the sensor and give the connectors a good cleaning. Hence if the sensor is having problems, then should be able to see the problem in the engine temp sensor on the dash/DIC set to engine temp. Simply, temp should start at zero when you first start the motor, than take about 5 mins for the temp to come up to around 210 at a steady rate. Any wild dips in the sensor is screaming either air in the system, while if the temp sensor or is connector/wiring is having problems, temp will drop all the way back to zero and bounce back isntead.

 

Agree with Dano. However the temp will start at ambient air temp and not zero. Great explanation as usual by Dano.

 

In addition to what Dano said, it could also be a ghost in the machine.

I've had this happen a few times on my '05 at ~90 seconds after starting when my battery has been failing. Same issue/msg a few weeks ago with the battery right before it failed again (even with a tender). I honestly don't know if this is two or three batteries, but you get the gist.

How old is your battery? How much have you driven it during the shutdown?

 

My Driver Information Center below the tach and spedo read "Low Coolant Level". That is why I checked it. Sure enough the coolant fill tank was almost empty.
I just put the car an a lift and discovered that the water pump seems to be leaking. Since the car has not been driven much I will keep a close eye on it. It appears to be a slow leak. I'm just glad it is not a head gasket.