Lincoln/Mercury Repair: 99 Lincoln Continental, head gasket, lincoln dealer

Question
Thank You for the fast response,  I have checked both oil and water neither show any signs of cross contamination, there is minor dripping of water from exhaust but no steam or anymore than normal for this time of year, it seems to stop quickly after start up.  The engine runs fine at idle for 30 minutes only overheats when rpm is increased after that.  ???
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The text above is a follow-up to ...

-----Question-----
"My mechanic replaced my water pump because it was making noise and the temp. would stay on the high end of normal.  After that he replaced the thermostat because it failed to open until temp spiked and would then open and be fine. I brought it back to him to fix this problem, he told me the head gasket was leaking. I took it to Lincoln dealer who said it was not head but the radiator and lower hose, they could not work on it for over a week so I brought it home and changed the radiator and hose, it still has original problem, it runs fine at idle for every, once rpm is increased about 2000 it overheats.  Do you think it is the head gasket, also if it is do you know if any sealers like Steel Seal or the like might work?
-----Answer-----
Hi Peter,

Check your fans. You have two, one which is theromstaticly controlled. They both come on when you have the a/c on. If the headgasket is leaking, you will see bubbles in your engine oil, even a icky white coating on your dip stick! Also, check the coolant to see if you have bubbles or oil in there. Also, water or white steam will be coming out of your tail pipe.

Answer
Well, we have to consider what the cooling system does and how. Obviously water is cooled in the radiator and returned to the engine. To see if there is flow, remove the cap on the radiator and let the engine warm up to operating temperature. Look in the radiator and see if water is moving. If it is not, and the gauge says hot, then one of two things, wrong or incorrect installation of new thermostat, or clogged radiator. If the water is moving but still overheating, then exhaust gases are super heating the coolant. This would indicate a blown head gasket. Blown head gaskets normally would leave other signs. The drip you see at the tailpipe is normal. Usually there would be steam, white smoke out of the tail pipe, or residue in the engine oil and coolant. I think he installed a bad thermostat but could be a clogged radiator. Check for flow and get back to me.