In early 2019 after 19years plus, the FactoryOriginal TStat housing on my 2001 Ford Explorer Sport Trac began to leak per the pics below; at first just an irritation, this leak steadily grew much worse. Under the Throttle on the TopFront of V6~4.0L~SOHC engines in several 1997~2012 Ford models, the Factory\OEM coolant ThermoStat housing is made of PPS Plastic, with the 2 SeparatelyMolded Lower+Upper parts joined using a Heated\Glued flange seam, notorious for leaking. My housings rear leaked into the "Cave" atop the engine under the Manifold, creating a smelly Coolant+Grime swamp. The various Ford part#s for these housings have similar LowerBodies; UpperBodies vary with 1 or 2 Threaded or Clipped Sensors; the TopCovers vary with RightHi\RightLo\ForeWard routed RadiatorHoses. After concluding any like Plastic replacement part will tend to leak just as the factory part leaked, I upgraded to an Aluminum TStat housing in 2019Aug with no leak as of 2020Dec & another 10k+ miles.

Minimal skill+patience, roughly 2 days, a level garage floor, & these basic shop items are needed for this repair:

* Hex+Torx SocketSet +DriverSet +Rachets +Adaptors +WrenchSet +SwivelExtensions
* ChannelLockPliers +NeedleNosePliers +ViceGripPliers
* WetVac +AirCompressor +ShopRags +PlasticGloves +DrainPan +DisposalContainers +AbsorbantLitter
* RTV Sealant, 700f371c Permatex#UltraCopper Recommended
* New Coolant, 2Gallons 50%EG 50%H2O Recommended

Parts & tools listed here are for this specific vehicle Year +Make +Model ...; do not assume they fit your vehicle; first verify your vehicle specs, closely inspect your engin & attached ThermoStat Housing, then confirm chosen vendor part descriptions\recommendations are appropriate before making purchase & working on your vehicle. Time to replace any other nearby parts: Hoses, Pump, RadiatorCap, Belt, Pulleys, AC\FanClutch, Tensioners..?

Old ThermoStat Housing REMOVAL+INSPECTION+CLEANUP

New ThermoStat Housing OPTIONS

Determined to not replace the old leaky part with a new leaky part, I found these options for improved housings. The aluminum ThermoStat Housing from SAS, pics & link below, appears the most rugid with Lower+Upper body machined as a single piece, minimizing potential for leaks; $130 ~ $160 depending on the accessories included. The SAS housing has EnginFlange guide tabs that can obstruct\break; bolts alone provide adequate alignment. The aluminum ThermoStat Housings from TAP \ SKP \ RAP \ GAP \ ZAB ..., pics & links below, appear alike as a group with Lower+Upper body joined by an ORing & 3Torx45Bushings, yet still an improvement vs the OEM part; $30 ~ $80 depending on accessories & vendor. SAS was too pricey for this "cheap bas'ard"; I chose the TAP kit with Valv +Sensors +Clips +ORings +Hose +Clamps +Bolts (less expensive SKP options became available later) then further improved this part with inverted TopBolts & RTV on the BodySeam +Sensor +EnginFlange ORings. After considering Threaded Sensors, I stayed with Clipped versions as room is limited under the IntakeManifold.

PICK ANY IMAGE ABOVE FOR A LARGER VIEW OR A VENDOR WEBLINK BELOW FOR MORE INFO.
* TAP# -254 +250
* SKP# SKRH144A\ SKRH144C
* RAP# CT83Y8\ N654WN\ Q562KW
* GAP# 18628-02010725\ 18628-02921819\ 18628-07741273
* ZAB# ATK-8592-ACCS
* SAS# SA3\ SA4 +SA5 +SA6 +SA7 +SA9

New ThermoStat Housing ASSEMBLY+PREP+INSTALL

Warning: Stant# 14748 ThermoStat LowerBypassDisc MUST BE GROUND NARROW slightly, to prevent jam open in the Housing throat & to take advantage of 4CoreAllAlumRadiators higher flow capacity.

New ThermoStat Housing SENSOR CHANGE+MOVE

In 2020Jun, while changing the TimingChain Tensioner located behind & left of this TStat housing, I removed the ClippedGray TempSensor on the TStat Housing, plugged that hole, drilled a new hole with a new ThreadedGray TempSensor as shown in the image below, which allows improved working clearances & access to the Tensioner.

Old ThermoStat Housing REBUILT

A few months after installing the new Aluminum TStat Housing, while doing some garage cleaning I came across the old Plastic TStat Housing; almost to the trash can, a question came to mind: might the Plastic BodySeam be taken apart & a root cause of the notorious leaks determined? After some 2hrs of gentle work with a razor knife, keyhole saw, brass brush, grinder..., the Lower+Upper body pieces were separated & cleaned, revealing a very weak GlueJoint\HeatSeal. Furthering this whim, pictured below is my ReBuild of the Plastic Housing as a backup. While I would trust this ReBuild more than a new Plastic Housing, an Aluminum Housing remains the preference.

Links To Related Info

Thanks go to the brave souls who've preceded me in similar adventures & freely shared their experience below:

http://youtu.be/wwOmoYgIYSE?t=20
http://youtu.be/fYp7_goQ2Qo?t=11
http://youtu.be/z31LuE6KDdg?t=1
http://youtu.be/4hna6iQHEw0?t=1
http://youtu.be/uUvlDJCreHc?t=1
http://youtu.be/CtogwA-ZJOw?t=1
http://youtu.be/lylAt1N_IBI?t=1
http://youtu.be/93aOMZ8om4g?t=15
http://youtu.be/6TcVOKXpyOI?t=2
http://youtu.be/wqkFLCbZ0R0?t=63
http://youtu.be/t57b-0ScZCw?t=1
http://youtu.be/Buyd-pMKQBk?t=78
http://youtu.be/mAcwuhFOuuo?t=59
http://youtu.be/eK8X7HAbzzg?t=39
http://youtu.be/H4jXC4MiDZA?t=47
http://youtu.be/bEJ-poFSPwA?t=1
http://youtu.be/sX5IhlnxGe0?t=1
http://youtu.be/sxGRjzB0tkQ?t=10
http://web.archive.org/web/20200809115410if_/https://www.explorerforum.com/forums/threads/possible-thermostat-problem-need-help.483910
http://web.archive.org/web/20200809115849if_/https://www.explorerforum.com/forums/threads/sohc-v6-replace-rebuild-or-remanufactured.438266
http://web.archive.org/web/20200301121249if_/http://howtoreplacefordthermostathousing.com/index.html
http://web.archive.org/web/20200323011029if_/http://www.naturecoastmustangs.com/articles/replacing_thermostat_housing_on_2005-2010_v6_mustang.aspx#page=0
http://www.sporttrac.org/search/7492435/?q=thermostat+leak&o=relevance
http://www.ranger-forums.com/search.php?do=showgcs&query=thermostat%20leak%204.0
http://cse.google.com/cse?cx=partner-pub-1465533425503040:2946757341&q=thermostat%20housing&oq=thermostat%20housing&gs_l=partner-generic.3...5849.9517.0.10110.0.0.0.0.0.0.0.0..0.0.gsnos%2Cn%3D13...0.3679j902503j18...1.34.partner-generic..0.0.0
http://www.ford-trucks.com/forums/search.php?do=showgcs&query=4.0%20thermostat%20leak
http://www.reddit.com/search/?q=v6%204.0L%20thermostat%20housing
http://www.solvay.us/en/binaries/Ryton-PPS-Mold-Temperature-205305.pdf
http://web.archive.org/web/20200920100659if_/https://www.explorerforum.com/forums/threads/stop-leak-coolant-additive-which-one.489558 Coolant Leak Fix: K-Seal
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