I have a 2008 chevy impala ss & it keep overheating i change the thermostat rely 2 the fan & got a diagnostic from the dealership, they nothing wrong then it overheats again, can u help me?

I see you replaced the fan relays but are the fans actually coming on ? If so flush cooling system with Prestone Super Radiator and Cooling System Flush just follow directions on product.

My 2008 Impala SS was overheating. At first I top off the resirvoir with coolant. He still overheated. I parked it and waited to move it until the next day to minimize engine damage. I drove it home the next morning and it overheated again. I later found out that the radiator cap was damaged bad and I was losing coolant. I identified the area of the leak. There was a leakage located bottom passenger side of the radiator. I went to the auto parts store and bought a new cap and a thermostat(based on my google experience) and a bottle of radiator stop leak. No luck. My SS kept overheating. I gave in and took it to the nearest radiator shop. Come to find out there was a crack in the plastic on the radiator tank. I had to get a new radiator and a thermostat housing. Not just the thermostat. New coolant. And like magic....no more over heating. See attached pic

I have a Chevy impala 2008 LT Automatic I'm having kinda the Same issues we just Replaced Both Sensors, and the Ratater Cap, we do have a small Crack on the Coolant reservoir could this Really be effecting why it Keep going up to the First Redline were going to try, and fix this and if that dosen't work maybe the Coolant Sensor Yes the Fans are coming on.

anyone looking at this I went through this bullshit. Its another problem that should have been recalled. You have to take cover off of engine compartment fuse box top off. Then I think its a 7mm socket you use to get the 4 fuse panel off. The 4 screwws loosen the 4 harness connections underneath. Take a screw driver if need be to pry the 4 harnees connections off. The problem is in the 3rd harness connection. take a small flat head screw driver and pry up on the two tabs(each side) on harness cap . after you do this you will see some melted wires. These need to be fixed. I tapped up the main power one. it got so hot it melted plastic coating off the wires. I went through same things as most of you have, freaking fans not working or intermittently, replacing fan relays, etc. You named it, i checked it. I hope this helped. good luck.