My Alero heats up when I stop at a traffic light. Everything checks out ok. No leaks, new temp sensor, etc. Any ideas?

More than likely the cooling fans or fan for the engine is not working, ether because of a fuse or the fan its self or the temp sensor that controls the relay for the fan. So first check fuse, then check the relay, then if those two are ok, then hook power and ground to cooling fan, if fan operates then ether the wire from fan to control temp sensor is open, or the coolant temp sensor if open, faulty, sense fan is not working this causing the a/c to be inop and the over heating of engine , but only at stop and go traffic do to the lost of air flow across a/c condenser and radiator.

if you are adding coolant every day then you are experiencing coolant loss
could be from a leaking pump gasket , head gasket or other leaking item
have a compression test done to check for head gasket , cracked head
next have the cooling system pressure tested to find the cooling leak
lastly check the fan, fan relay , fuses and coolant temp sensor unit for correct operation

If you have a viscous fan hub then have it replaced as it is not drawing air through the radiator at idle or slow speed (crawling traffic). Check that are no air locks in the system as they will cause heating problems.

Sounds like the head gasket is leaking

Thanks for choosing FixYa and welcome. Since your check engine light is on, take it to Autozone or Advanced to have it scanned. This light is on because the computer has detected a problem with your vehicle. You need your computer hooked up. It cost nothing to have this done and they will tell you what is wrong, which can solve your issue without guessing. You could have a clogged fuel filter or air filter. Check to make sure there are no vacuum leaks also. Make sure all wires and hoses are hooked up. Sounds like it may be air related. You could have a bad 02 sensor. Get the test done. There is a good chance it will show what is wrong on the computer. No sense waisting your time and money when you don't have to. Like I said, they do it for free and it only takes a few seconds to run the test. Hope this helps. Ricky

Check that you have'nt knocked the terminal block off the speedo sensor which is on the back of the gearbox housing,Just above the N/S inner driveshaft joint

is cooling fan coming on?? the coolant level light pertains to a sensor that is in radiator side tank that is notorious for going bad you may have two seperate problems normal temp at high speed tells me the wind passing across radiator is keeping cool when stopped or in traffic as temp increases pcm commands fan to come on if it does,nt you will heat up

Check your radiator fan is cutting in when it's supposed too Sounds like that the cause is no air flow when you stopped or in slow traffic

sounds like a thermostate problem for the over heating would have to no more info for the cost aspect

intake manifold has a vacum leak or other vacum leak hose etc.