@aol.comI have already had my coolant system replaced. 1.5yrs. later my check coolant light comes on. What should I do. Try to refill?

Is it running at the right temperature and is there coolant in the system and has it been refilled recently?
Possible reasons are the sensor is faulty, it really is running hot or there is an air lock.
Also look at the connection to the coolant sensor, check its not corroded.

IF the coolant is at the proper level and the light is still coming on, you will need to replace the coolant overflow resevoir. The sensor for the level is built into these. If your just looking to get your light to go off, try unplugging the two wire connector from the overflow bottle (located at the bottom) and see if the light goes out. If its still on, you can try jumping those two pins together with a paper clip. Keep in mind if you bypass the light, you won't know if your actually low on coolant. My recomnedation would be to order a new one since this is a common problem on this vehicle.

Most probably when the radiator was replaced it was not filled properly and you have an air lock in the system preventing water from circulating properly.
Read your owners manual or go a forum on your partcular car there as specific methods of adding coolant to assure no problems. Some systems even have a bleeder.
Other possible problems would be a collapsed hose or a bad thermostat.

check that the system dose not have a bleeder valve to let the air outof it.and some times the sensor onthe over flow tank will stick try tapping lightly on tank

Your Malibu is too new to change the coolant already The coolant is good for 5 years or 150.000 miles, which ever comes first. If oyu are going to replace the coolant, make sure it's the orange coolant and premixed 50/50 water/coolant before refilling the radiator.

To drain the coolant, just disconnect the lower radiator hose. most radiators now don't have a drain plug like the old days. The issue was that the drain plug was breaking since it's plastic or the O rings would break causing fluid to leak from the radiator.

once the radiator is drained, simple reattached the lower radiator hose and refill the system. The other way would be to run the engine till the thermostat opens up and the rest of the coolant in the engine block will make it's way out, but at most you should be fine on to replacing the coolant at the radiator only and then run the engine to ensure you have got all the air out of the system.

Just make sure you replace the radiator cap first before you shut the engine down. It you do shut the engine down first before you place the cap back on, the coolant will blow out.

Thank you for using fixy and be safe.

The radiator has a screw in sensor which can be at fault. I would replace that first

I assume you have already checked coolant radiator core for blockage and airflow obstruction, and the engine does not have other mechanical or tune-up problems.

A complete radiator /engine block flushout may be worthwhile if you are in any doubt.

Check there is not a collapsing (soft) hose on the intake side of the waterpump when engine speed above idle,
Check your cooling fan/s are working correctly,
Check the coolant system doesn't have an air lock, resulting in incomplete coolant fill - perform any necessary air bleeding during system refill,
Check the coolant pressure cap is in good order, and of correct specification and type.

try to get a bottle of transmission sealant first, or sometimes called stop leak. add that, see how it goes for a while. if happens again, then look at hoses and connections, if still happens maybe radiator or a puncture some where

Sure, but you have to be able to handle the contents of the coolant system (roughly 2 gallons) and be prepared to refill it with fresh coolant. To replace it, drain the cooling system first. Remove the top radiator hose from the thermostat housing at the top of the engine. Remove the bolts holding the housing to the engine and then pull the housing up. It may be stuck and you will need to pry it up gently. Do not use a screwdriver under the housing to pry it as you will gouge the metal and cause a leak later. Often a few soft taps from a rubber mallet will loosen it. Note how the thermostat spring is set in the housing as that is the way the new one will go. You will need to remove all of the old gasket material and avoid letting it get dropped into the engine opening. I stuff a shop towel in the opening before I start scraping with a plastic scraper -again this avoids damaging the soft aluminum. Once the old stuff is out, put in the new gasket, put the thermostat in (you will have already bought it and have it on hand) cinch down the bolts to be snug but not overly tight as they can strip easily. Replace the hose (maybe with a new one since you've done the hard part?) and then refill the cooling system and test run to look for leaks. You will need to get the engine up to normal temp to allow the thermostat to begin working. Might as well change all radiator hoses if they are more than 3 years old at this point. Otherwise you will be draining the coolant system again to do it later.

Have fun with it.

make sure your coolant fluid level is good, than check the valve that controls the amount of coolant that flows to the heat exchanger inside your dashboard, make sure it is wide open. (find it by having someone inside the car move the heat control from hot to cold and back while you are under the hood looking for the valve. Sometimes the cable that goes from the dashboard heat/temp control to the coolant valve comes off.