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 2021Feb & 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..?


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.

* TAP# -254 +250
* RAP# CT83Y8\ N654WN\ Q562KW
* GAP# 18628-02010725\ 18628-02921819\ 18628-07741273
* ZAB# ATK-8592-ACCS
* SAS# SA3\ SA4 +SA5 +SA6 +SA7 +SA9


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: Coolant SystemLeak+PressureTest Coolant Leak Fix: K-Seal
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