2002 Impala leaking antifreeze near the tstat housing

Hello,

If you have coolant leaking from the housing, your housing gasket is probably bad. With engine cold, drain some coolant out of your radiator, remove upper hose from housing, unbolt housing from engine (3 bolts if I recall correcty), remove old gasket and clean area well, install new gasket (around $2 or 3 dollars at any autopart store), and put everything back together. Add coolant in your radiator, and squeeze upper hose a few times to get the air out (add coolant as necessary). With radiator cap off, and bleed screws open, turn car on and check your bleed screws; when coolant start pouring out of screws shut them. Add coolant in radiator if you can and put cap back on when coolant starts coming out. Let your car warm up until it reaches normal operating temperature. Check your housing to make sure it doesn't leak, then shut the car off and let it cool down. With engine cold, open radiator and add coolant as necessary. You may have to do this a few times before the system is full and free of air.
Anyway, it's not a difficult job, but removing and installing the housing can be a pain in the butt. Also, personally I always add some RTV sealant with my gasket just to be absolutely sure there is no leak even after I put the new gasket on. If you do that you'll have to let the sealant cure.

An intake manifold gasket is very common problem and an updated gasket kit is needed