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Coolant leak; thermostat housing suspected


RegularGuy

Well-Known Member
Joined
Apr 20, 2020
Messages
129
City
Belingham, WA
Vehicle Year
2007
Engine
4.0 V6
Transmission
Automatic
Found my reservoir and rad nearly dry tonight while replacing my front shocks. Theres coolant running down the front of the head on the passenger side burning off on the passenger side manifold and liquid pooled in the valley (don't know if that bit is coolant or just water).
The three options I'm seeing here in order of most, to least probable: A cracked thermostat housing (In which case I'll swap it for an aluminum), I missed a hose connection, or a blown head gasket (which somehow is only affecting the water jacket)

The Question: There doesn't appear to be a ton of space around the thermostat housing, so how should I go about inspecting it? Am I stuck removing the assembly or is there something easier to remove that would allow for inspection without digging the housing out the vehicle?
 
Removing the throttle body will allow a better look at it, but typically you need to remove the intake manifold also to get the thermostat housing out because of the temperature sensors. The model year 2007 may have only one sensor and there may be room to get it out without removing the intake manifold.
 
An endoscope camera attached to your stupidphone would help inspect the tight quarters around the ThermoStatHousing.
Description of coolant in the engine valley is a near 100% confirmation that the ThermoStatHousing is the leaker.
If it's never been replaced, now 14+ years old, it's done it's duty. Aluminum is the way to go.
I'd replace any other Coolant system component that is as old, while your doing it.
Consider replacing the OilPressurized TimingTensioners if they're more than 75kMiles old, while the ThermoStatHousing is out of the way.
Click here for more info on the ThermoStatHousing.
 
I have a bit of an update, earlier today I found moisture on the housing, as well as small amount of pooling atop the power steering pump bracket.
Having shoved my phone under the throttle body, I was able to get this image...

20211208_132800.jpg


Notice the moisture along the plastic welded seam, and on the aluminum mount.
 
Good that now you've confirmed problem & now know that you need a new TStatHousing.
First removing the SerpBelt & IdlerPulley (easy to do)
makes getting TStatHousing & the short ByPassHose removed+replaced quite a bit easier.
Again, consider replacing any other Coolant system component that is original or 10+years old while you're doing this.
 
First half of the parts arrived today, but the thermostat is kinda funky looking... Know if this is correct for the 2007 4.0L? The thermostat doesn't match the pictures online for the part number. Not really wanting to tear into the engine without all the parts present in order to find out

20211214_202924.jpg20211214_202936.jpg
 
I thought as much.... I got the private label off rockauto. Best as I can tell, the wrong part was in the box. I'll see about getting it swapped out
 
That doesn’t look like any thermostat I’ve ever changed.
 

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