I have a 1993 Chevy Lumina 3.1 v6. The low coolant light stays on even when the coolant is full. I bled the system and changed the thermostat and still doesnt go off. I have also noticed that if i go on trips and try to check the radiator, the coolant doesnt spew out like it should. Do u know what would cause this and what I could do to fix it?

No. The most common problem with the low sensor light is the switch which is located in the radiator just below the filler neck. First make sure that the radiator is full. With the cap off, start the engine and then add coolant to the radiator. There are two bleed valves in the system. One by the thermostat area and the other by the by-pass hose close to the water pump. Be sure all the air is out of the system. The low coolant sensor gets dirty and causes this problem.

Its not the expansion tank you need to look at. Open the radiator cap when the engine is cold. Coolant should be right at the top. Was all the air bled from the system when these components were replaced? If the system has air in it, it will not effectively cool. Was the thermostat installed correctly? ( Put in backwards ). Electric rad fan? Is it operational?

In most newer chevys, the coolant reservoir is part of the pressurized system. Rather than just holding overflow coolant and relying on the radiator pressure cap to draw from and expel to the reservoir, it is an active part of the cooling system. On these systems, there is a coolant level switch in the reservoir. This will activate if the level in the reservoir gets below a certain point. So it is possible to have a full radiator and still get a low coolant light. Be advised that as the reservoir ages and get stained, it is not uncommon for the low coolant sensor to give false indications of low coolant.

Is the radiator full? make sure there are no air pockets in the engine block. Check the coolant level often.

You need to repair the low coolant condition before any more diagnosis. If the coolant in the radiator is low that's what the light is telling you. You may have a coolant leak. fix that first then make sure the cooling system is full. Use coolant (50/50) not water.

Coolant level sensor failures are common. It is located in the radiator tank on the right (passeger) side of the radiator. it looks like the picture below. Also, there has been a lot of problems with the connector for these sensors. (see picture) AutoZone stocks BOTH of these parts. Inspect the connector for breakage, corrosion and insulation peeling off of the wires. If there are no problems found with the connector, then you can probably just replace the sensor.

When filling the coolant system you need to have the car running with radiator cap off and you can also burp the coolant hose while filling the system to remove any air. The system may be full for a while until thermostat opens and sucks the coolant out of radiator which is the perfect time to add more to top it off.

Disconnecting your negative battery cable for 10 minutes will reset the computer and shut off the light.

you dont "bleed" a motor.... chances are you have a faulty coolant temperature sensor, thermostat, or water pump

Does the low coolant light come on?

A radiator cap with a bad seal will allow the coolant bottle to stay full but the rest of the coolant system to get low. Water pumps on the V6 engines will leak only when the engine is running. But you will find coolant on the right side of the car. If you do not see coolant on the ground where you park it could be the intake manifold gaskets leaking. This has been a big problem for GM, run a Google search. You can take it to a service center and they can test the system and tell you where the coolant is going.