Car keeps overheating on 2000 Lincoln LS

I have a Lincoln LS 2000, just got it back in June '10, well car was running great, till a few months ago that it heat it up, I changed the thermostat, water pump, a couple of plastic hoses (broken) and it keeps overheating. Do I have to go directly to change the head gasket to keep car from this problem? other than that, car runs great.

2 answers 2 comments
You can have a shop do a 'block test' or test your coolant for any exhaust gases with the 5 gas analyzer in a Smog machine. That way you will KNOW if the head gaskets are bad.
Thanks will do the test ASAP.
This engine has a hydraulic cooling fan motor, which definitely could have an issue. I would have the cooling system assessed in whole before doing anything else.
Thanks DaveJHM will check the fan and cooling syst. hope that if its the fan, it can be repaired, darn thing costs $800 dls.