i recently replaced the head gaskets in my 2001 subaru outback it ran great for a week and half now it over heats it does not boil over temp gage just goes to red after drivein about 7 minutes

Make sure the cooling fans are working. Did you flush out the engine after the head gaskets were replaced?

BE ABSOLUELY SURE that your "replacement" t-stat was either OE or same big orifice as OE. Smaller bore aftermarket t-stats are infamous for restricting coolant flow under load (hills or high speed), causing overheating under stress. As likely, you have an errant air buble in the system that occasionally "settles" near the temp sensor, momentarily causing it to spike upward. So when cold, see if you can add coolant to radiator; squeeze upper hose to help purge its volume. Even park with front HIGHER, so that trapped air in rear heater hoses also "burp" forward and upward and eventually escape through the rad cap. Note that some of us have had to "burp" trapped air several times after changing coolant. A decent highway run between purging sequences helps dislodge trapped air pockets. So ensure your cooling system is fully purged. If there's still an overheating problem, check that "new" t-stat (interestingly, the big OE t-stts NEVER fail!). If still problematic I'd fear a blocked passage, so BACK-FLUSH those rear heater hoses in case they're blocked with old scale particles. If none of this works, and coolant flow seems normal, then I'd start to look at the quality of the HG job (loose head bolts, failure to "tank" and "plane" the heads at a machine shop, resulting in poor sealing, etc. Good luck...I'll bet you're just insufficiently purged, have a small t- stat, or blockage in the hoses or rad from a goopy additive or scale...simpler stuff.

Oh yeah...make sure the fans work. Thanks FoR!

the fans are working could it be the head gasket even if there are no oil antifreeze mix??? and is it normal to run perfect for a little over a week and have air bubbles?? its pushing the antifreeze out in to the overflow

It can be "normal" for trapped air bubbles to percolate out of the coolant through the expansion tank, but that should subside as the system self-purges. If not, I suspect a head gasket gap allowing pressurizing the coolant FROM the combustion chamber TO the coolant bath...and not involving coolant/oil interface. Have a wrench use a sniffer to differentiate air bubbles from HC- infused exhaust gases at the radiator neck while hot-idling and occasional revving to produce bubbles (have AC on so that cooling fans keep system isothermal so that coolant level stays relatively stable so you can watch activity at the neck; use a tight funnel mounted into the rad neck and slightly overfill with water/coolant to provide a nice wide viewing "puddle" to watch/sniff bubbles. Good luck.

boxerluver76- Don't be afraid to consider taking the car to a good independent mechanic, if nothing more than to check out your systems and make sure things are back to normal. I'm sure that your 2001 Subaru Outback Limited is nice and you want to get that back on the road with no problems? Do you have the automatic or manual transmission? And, do you have a lot of miles on this car?

What if now the fan is stuck on

Which fan?