truck still overcooling new therm, and new fan clutch?

Someone I know had the same problem with his Ranger.He slipped a large piece of cardboard in front of the radiator for the winter and it really helped.

What are the air temps in your area?...very cold ambient air can can make the engine take longer to warm up or keep temps at lower levels than normal while driving. Some people block off a third to half the radiator with cardboard to help engine warmup faster and maintain warmer temps in cold weather.At highway speeds in cold temps, the radiator wicks away heat faster than normal which keeps engine temps lower than normal in warmer weather. I'd say to check the coolant temp with a kitchen thermometer in the radiator neck to see what the actual temps are....run the engine for 10- 15 minutes or so and check....should be around 195-205 degrees if normal. If lower than that and air is cold, block off part of the radiator and retest after a few minutes of idling or road test. The radiator cap may be bad which is not holding pressure in the system...low system pressure can also cause lower than normal coolant temps.

You might also have an air pocket in the head, system hoses or heater core which can cause low temps, temp variations/fluctuating gauge or poor heater function...always bleed the cooling system of any air pockets after any repairs or low coolant level. I'd start with that.

The t-stat may also be sticking / defective or incorrect style...use a genuine Motorcraft one...is it installed properly?...not upside down?

http://www.rangerpowersports.com/forum/f11/temp-ga...

http://community.cartalk.com/discussion/2116327/lo...

"The first thing I would suspect is that you have the wrong thermostat. I have through personal experience learned that a genuine Motorcraft thermostat is the only way to go. The aftermarket ones are NOT designed specifically for your truck. They do not bleed the air properly, which can lead to strange thing as trapped air can prevent the coolant from flowing correctly. A Motorcraft thermostat does not cost significantly more than any other brand, but they work properly, and they are made for your specific truck.

"

http://www.ford-trucks.com/forums/1031950-heat-goe...

when the engine is warmed up feel both heater hoses, both should be hot ! if they are hot then it,s circulating ! if you can drive it then take the cap off with no pressure then it could be you got the wrong temperature cap and it,s not holding pressure ! once the engine is hot is the reservoir reads on the hot mark like it should ? did you check the oil to see if any antifreeze is in it ? you know what i am driving at, don,t you ? i am thinking it might be the head or intake gasket leaking and letting it not hold pressure !

I see you have done everything except to hang a thermometer in the coolant. The fact that you don't have any pressure build up doesn't tell me anything except that that cap you have is wrong.

if your thermostat didnt open, youd have burnt this thing into the ground long ago, regardless of the fan,etc. coolant has to circulate or it overheats. i question the accuracy of your gauge.