99 GA GT Overheating!?

I have a 1999 Pontiac Grand Am GT that I love!! But, it's over heating and I don't know why?? I replaced the water pump, thermostat, had the cooling system flushed, had the radiator and the head gasket checked, and nothing is wrong!! But its still over heating, I noticed that when it does over heat, anti freeze is coming out of a thing that has a black cap and wires on the top of it. This thing is located next and just below the little brake fluid container. Its the 3400 6cyl engine and i heared that the thing is a temperate control sensor holder or something and the gasket is broke? Or something? Does anyone know what's going on?? Please help, I love my car and got alot of money in it. Thanx! Robin.

Welcome to AF !

Could just be an air pocket trapped in the cooling system. Do you notice if the heater works ?

Sometimes when it has air trapped in there , it starts to over heat the heater will start to blow colder air because of an air pocket getting trapped in the heater core.

Thier is a procedure on bleeding the cooling system in the Tips and Maintenance (http://www.automotiveforums.com/vbulletin/forumdisplay.php?f=2148)sub forum.

How hot is it actualy getting ??
At 223-225 deg one of the cooling fans on the radiator should kick in, and at around 230+ both kick on. At around 245-250 deg the engine should shut its self down to protect it from damage.

Hope that helps!

I found the problem!! My antifreeze was spraying out of a hose!? OMG! I probably wasted money replacing parts that didnt need to be replaced! Thnx n e way!!!