Can I add coolant directly to the radiator? I can't find such a cap -- I can only see the overflow reservoir and cap. I have a 2002 Jeep Liberty

There is no "radiator cap" on the Alero. It has a pressurized recovery tank (overflow bottle) integrated into the cooling system. Unlike other cooling systems where you can add coolant to the coolant reservoir when the engine is hot as there is no pressure in the reservoir, these tanks are at full system pressure and must be allowed to cool down in order to check levels and/or add coolant. This is the only place in the system that allows for coolant input.

are you confused?
does the operators manual show 2 tanks.???marked AF, antifreeze?
is one, washer fluid.?
it look it up in the FSM but no engine stated.
http://www.amazon.com/2002-2007-Radiator-Overflow-Reservoir-Mopar/dp/B00E8PPE4A

i see one tank ,called BOTTLE here,
my guess is you lost the operators guide and are lost.
http://www.factorychryslerparts.com/showAssembly.aspx?ukey_assembly=612242&ukey_make=1064&ukey_model=15531&modelYear=2004&ukey_driveLine=7453&ukey_trimLevel=18498&searchString=tank

Hello Michelle, my name is Michael and I too had air in the cooling system and this is how I got it out. I had to raise the front end to where the middle of the front bumper was about 40 inches. I removed the radiator cap and immediately had ton add more coolant till it was visibly full at the radiator filler neck. Make sure the cap on the overflow reservoir is on tight. Now start the car and observe the filler neck because you will probably have to add more coolant. once it is full turn on the heater to the max position and direct it to the feet and econ. you should see a lot of bubbles coming from the radiator filler neck. That is the air being purged from the system. make sure you fill with coolant as needed. Now when the t-stat opens you'll see the coolant drop from the filler neck because it's being exchanged from the engine block do not add coolant at this point. Put the radiator cap back on and remove the screw holding the overflow reservoir and raise the reservoir above the radiator and squeeze the tube to get the air out of the tube. Once the air is out and the tube is filled with coolant put the reservoir back in place and fill with coolant to the FULL mark. Shut off the engine lower vehicle and let the engine cool down and remove the radiator cap and fill with coolant till it is visibly full and replace the radiator cap. I had to do this twice but it worked and my car is operating at normal temperature and with the same stroke took care of a few other problems. Hope this helps and good luck to you.

a leak in coolant system will cause air pocket in the coolant system around the engine coolant temperature sensor.coolant sensor is a thermistor in which when hot cool cause it resistance decrease which affect the voltage from sensor to pcm which will cause engine coolant to turn on.if coolant level okay,check coolant fan fuse and relay, if all is good,engine coolant temperature sensor could be bad or have vechicle code scan for pcm problems it control the coolant fan.fill coolant system to correct level make sure engine coolat reservoir is at full cold mark and not empty.fill coolant system check for leaks,refill coolant overflow jug back to full cold mark dont over fill, if coolant overflow stay empty you have leak either its leaking or you have radiator hoses or radiator leaking coolant.when coolant overflow jug run dry it cause air get in coolant system causing overheating problems.

you can buy after market radiator coolant bottles at auto part stores.

Yes, coolant is added in reservoir, no radiator cap

Add coolant 50 / 50 mixture water to coolant in the overflow resovoir...

The radiator is that flat panel shaped object in the front-most center of the engine compartment. You don't add coolant and water directly into the radiator. On the right side of the engine compartment is a plastic overflow reservoir with a blue cap. That's where the coolant/water mix goes. Run the engine while adding coolant and water. There are fill marks on the reservoir indicating how much coolant/water mix is required. With the engine running, if the radiator is very low on coolant it will repeatedly draw fluid from the reservoir. Continue to add coolant/water mix until the situation stabilizes and the reservoir is filled to the high fill mark.

you drain it from the radiator petcock on the bottom and you fill it from the overflow tank however I seem to remember those cars as having a radiator cap if i'm not mistaken it is on the passenger side if not in is the overflow tank

either a leaky head gasket or someone put oil in the overflow, it happens, clean it out drain the coolant from the entire system and refill with new long life antifreeze, also add a can of good radiator sealer.