Antifreeze on top of engine

[Steven111]

2006 Explorer Eddie Bauer V6 220,000 miles

I've had 4 radiators and a water pump in this thing in the 2 years since I bought it for my college-bound daughter, installed by 2 different service centers. Just when I hoped my cooling system problems were over....well....

Saw the coolant level was down and thought "not again" and looked for the typical radiator leaks. But not this time.....found coolant puddling on the top of the engine, behind the thermostat housing, where it looks like there are 2 soft plugs.

Hoping it was the thermostat housing gasket, I wiped away all the coolant from the top of the engine, topped off the coolant, and fired it up and let it get warm and start pumping coolant (top hose got hot) and in 15 minutes of idling did not see any leak! So I drove it about 3 miles at highway speed and then popped the hood -- ah ha! -- there was about a teaspoon of coolant puddled in the front and rear of the top of the block, beside the front soft plug, and behind the rear soft plug.

I could not see any leak from the thermostat housing, but I can't see where the leak is coming from, either.

It seems to only leak at highway speeds -- does this make sense, due to higher internal engine pressures or something?

Am I looking at a head gasket? There is noting in the oil and it runs smooth.

I feel like I am so screwed with this vehicle......

Thanks in advance for any advice/ ideas.

 

[Old As Dirt]

There is a sensor (computer) on top of the black thermostat housing near where the top radiator hose attaches. Carefully pull out the spring clip that holds it in place (I lost one under the intake manifold somewhere and had to replace it - hold onto it with needle-nosed pliers - the clip pulls out toward the passenger side) and pull the sensor up. Go to the hardware store and replace the "O" ring. Replace the sensor and the clip and you're good to go. Wash the top of the engine with clean water because the anti-freeze will not evaporate and that gets rid of the stink.

 

[fritz24]

Dont pull the sensor. You cant see the leak if it is the bottom gasket of the housing and is only leaking from behind. Could also the lower housing is warp.

 

[Davidm53]

I spent the extra money and replaced the housing with the steel version found on EBay. The previous plastic housing only lasted a few weeks even with proper torque on the bolts.

You might consider a 16 PSI radiator cap if you don't already have one.

 

[Steven111]

Thanks!

If it is not the t-stat block what else might it be?

 

[Davidm53]

If it's not a obvious leak somewhere and hard to find, best thing to do is a pressure check of the system.

 

[swshawaii]

Ditto above. Rent a coolant system pressure test kit with a fully refundable deposit. Small mirror and light sometimes works in a pinch. Closely inspect the rear of the lower thermostat housing where the welded seams split and leak. VERY common failure with
the 4.0 SOHC. Here's just one thread from this 2006-10 sub forum, there are MANY more, do a search. GL

Coolant Leak - puddled on top of engine
http://www.explorerforum.com/forums/showthread.php?t=340734&highlight=lower+thermostat+housing

 

[Accarguy]

save your time and replace the entire t stat housing, you cannot really see them leaking. Just the valley fills up with coolant. The plastic warps over time from the temp cycles so you are better off replacing it all then trying to throw little parts at it. They are not that difficult to change any way

 

[Davidm53]

16 PSI Cap, is easy and inexpensive also.

 

[Steven111]

Ditto above. Rent a coolant system pressure test kit with a fully refundable deposit. Small mirror and light sometimes works in a pinch. Closely inspect the rear of the lower thermostat housing where the welded seams split and leak. VERY common failure with
the 4.0 SOHC. Here's just one thread from this 2006-10 sub forum, there are MANY more, do a search. GL

Coolant Leak - puddled on top of engine
http://www.explorerforum.com/forums/showthread.php?t=340734&highlight=lower+thermostat+housing

Thanks -- who rents these -- auto parts places?

 

[swshawaii]

Thanks -- who rents these -- auto parts places?

Most larger auto parts chain stores offer loaner tools, call around for availability. Wanna bet it's the lower t-stat housing? GL

 

[Tech By Trade]

Dorman makes a quality replacment for around 40 bucks. I bought mine off amazon. Top and bottom. It has lasted 2 years and been removed 3 times with no issues. once during my timing chain fiasco, and once for the thermostat replacement.

 

[MotorCityFats13]

my t-stat housing was leaking pretty bad when I bought mine used in december... replaced it with the $20 ebay special problem went away but I did notice that the o-ring on the temp sensor was really loose so I matched it with one at a hardware store and have not had any problems... also replaced the bolts and cage nuts with longer bolts and nuts to pinch all 3 sections together unlike the factory setup that only pinches the neck and middle section leaving the bottom able to split apart

 

[Steven111]

Thanks everyone for your help!

Gonna get the pressure test kit and try it this weekend.

Does the Dorman part come with all the needed gaskets, etc. or do I need anything else?

 

[Steven111]

Y'all were right. Pressure test showed a leak at the seam of the t-stat housing in the back.

 

[Steven111]

I'm swamped in middle of a home remodeling project now, so I got a quote from my mechanic -- $420 to replace this thing!

Is it a pain or what? I can get the part for like $60 so not sure why the high quote. Any ideas?

 

[Flag Gibby]

Nope, not that difficult to replace. Takes about 30 minutes including draining some of the coolant out of the system. Just be sure to not over tighten the bolts on the new assembly.

 

[MotorCityFats13]

bought mine for $20... and swapped it out in my parking lot at work in like 20 minutes when it was freezing temps 20 minutes before sun down... probably would be faster in day light and warm temps... everything is in clear view.... hardest part for me was that stupid clip holding in the temp sensor... the stock clip didnt get along with the housing I bought and i had to grind it down some