My 2004 Ford Explorer 4.0V6 overheating,Is there a Definite Fix?Intake/T/housing on 2004 Ford Explorer

I have read a lot of blogs in other Forums. My 2004 Ford Explorer has the 4.0 V6 Flex Fuel Engine. The 8th digit of the vin is "K". I replaced the Whole Thermostat housing including new t-stat and gasket. The part came with o-ring for under t-stat housing to engine,which was already installed.Also had t-stat & t-stat gasket and a small o-ring I believe is a new one for the Temp sensor that goes in top of t-stat housing.I have only one sensor so I used the plug(came w/ housing)for the other hole.Followed Coolant bleeding instructions from Chilton Repair Manual exactly as it explained.Now, The temp will stay Normal around town but as soon as I go on the Highway the needle shoots up to Hot.The check gauge comes on and the coolant is boiling in the coolant Tank!T-stat does open and Top hose gets Hot. Also idles like crap which it did not do before.I don't like the No radiator cap design!I have tried everything. I know the way the coolant system works that is why this is confusing!It doesn't make sense the way that it overheats.If I let it sit at idle, there are no problems.The needle stays in the middle were it is suppose to be. Any help would be appreciated.

by in Newburyport, MA on August 05, 2013
2 answers 3 comments
ANSWER by on August 05, 2013
Since you have correctly installed stat and purged all air...Possible radiator restriction. Also suggest getting a combustion leak test performed If you want to know, for sure, if you have a head/gasket problem!!! Check coolant level before starting engine in the morning, or while engine is cold, to see if more is needed.
COMMENT by on August 26, 2013
Pushrod & Goodguy, I am still being challenged by this Ford!I have done a lil more since Ive posted last.I have flushed system FULLY(even taking off each hose to make sure no clogs).Replaced Coolant Tank CAP(No Radiator Cap).Removed PLASTIC INTAKE(Poor Design)& replaced Lower Intake Gaskets.Put it all back together,double checking Everything I unplugged or took off or disconnected.Filled Coolant System with correct 50/50 coolant.Said a little Prayer and Turned the Key!It Started right up,No Problem.The next morning I came out to check coolant tank,almost empty.WTF?So I filled tank & drove around.Once it heated up,the needle would float a lil bit till it finally went all the way to HOT & the check gauge light came on.Turned motor off Immediately.I tightened Intake bolts again after the motor cooled down.Nothing is Leaking But I think the coolant must be going out the exhaust when i'm driving.I see white smoke once in awhile not a lot & it goes away.Also SOMETIMES it has erratic idle/hesitation.When thats not happening it runs great. Smooth like it's suppose to.Any Help would be appreciated.My best educated guess is I have a cracked valve.By the way I did a coolant pressure test & it held at 16psi.That should of found LEAK if there was one....correct?Also the cooling fan is working correctly.
COMMENT by on August 26, 2013
COMBUSTION LEAK TEST NEEDED!! Any repair shop SHOULD be able to do it.
ANSWER by on August 06, 2013
does it have an electric cooling fan if so is it working if no fan then I agree with pushrod and check for a head gasket problem
COMMENT by on August 26, 2013
Pushrod & Goodguy, I am still being challenged by this Ford!I have done a lil more since Ive posted last.I have flushed system FULLY(even taking off each hose to make sure no clogs).Replaced Coolant Tank CAP(No Radiator Cap).Removed PLASTIC INTAKE(Poor Design)& replaced Lower Intake Gaskets.Put it all back together,double checking Everything I unplugged or took off or disconnected.Filled Coolant System with correct 50/50 coolant.Said a little Prayer and Turned the Key!It Started right up,No Problem.The next morning I came out to check coolant tank,almost empty.WTF?So I filled tank & drove around.Once it heated up,the needle would float a lil bit till it finally went all the way to HOT & the check gauge light came on.Turned motor off Immediately.I tightened Intake bolts again after the motor cooled down.Nothing is Leaking But I think the coolant must be going out the exhaust when i'm driving.I see white smoke once in awhile not a lot & it goes away.Also SOMETIMES it has erratic idle/hesitation.When thats not happening it runs great. Smooth like it's suppose to.Any Help would be appreciated.My best educated guess is I have a cracked valve.By the way I did a coolant pressure test & it held at 16psi.That should of found LEAK if there was one....correct?Also the Cooling Fan is Working Correctly.