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.

 

4.0 has a mile of hoses and a POS plastic t-stat housing that cracks and leaks. Both are suspects, and are so bad that they are subject to "stop and frisk" actions.

 

Check the top of t-stat hsg around sending units. Hsg. could crack and seal up when hot.

 

Thanks, guys!

But I watched that area from the time it was engine cool until 15 minutes after the t-stat opened and never saw a drop of coolant come from that area around the t-stat housing.

The only time I saw coolant was after driving at highway speed. and then popped the hood and saw some accumulation, but never could tell where it came from.

Lemme ask this another way......if it is not associated with the t-stat housing what else is the likely culprit?

Thanks!

 

I had this same issue and it was the thermostat housing. But it wasn't cracked, it was simply warped enough that it wouldn't seal properly. The leak only happened with a load on the engine and the housing would change shape enough that it leaked out between the seal, perhaps due to increased pressures and flow. Otherwise, no leak when it just idled.

I replaced the thermostat housing, sensors, gaskets (including the sensor gaskets) and the intake manifold gasket and the problem went away. But that was just my experience. I'm not saying it couldn't be something else.

 

Thanks for the input.

Gonna try a pressure test and see if I can see it leaking there. But of course it is a high point on the engine so.....that might be hard. Sigh....

 

Because it might leak air instead of coolant? Actually, it might make it easier since air tends to leak faster than coolant. Spray some soapy water on it and see if it makes bubbles.

But sometimes the temperature change is required to make it leak.

 

You guys are genius -- did a pressure test, started leaking at 5-10 psi on a seam in back of the t-stat assembly.

 

I'm swamped in middle of a home remodeling project now, 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?

 

That doesn't sound like it is out of line if you have a trusted mechanic that replaces other parts, too. There are more parts involved than just body itself. The sensors, gaskets, hoses, thermostat and bolts could or should be replaced at the same time. I spent about $270 in parts when I did it on mine (that was discounted Ford Motorcraft parts from Rockauto, not retail, and not aftermarket parts).

Although the thermostat is easily seen, it is not so easily replaced. I had to remove the upper intake manifold (the plastic one) and all that was connected to it.

By the way, be glad Ford redesigned the thermostat housing and sensors. The housing for my '99 was listed at $420! But I converted to the new housing which is only $60. But that also required me to get the newer sensors (for a 2000) which were still electronically equivalent.

 

I just did one of those a couple months back, IIRC it was just under $300 out the door.
Figure a 100% markup on the part price, plus labor of about 1-1.5hrs, and you're easily at $250-$280 before tax. $400 plus sounds like a dealership price, they are too expensive to take anything not under warranty to.

 

They are simple to change! I believe part of the problem with 4th generations engines is they run a 20 pound radiator cap.. This is asking for trouble with the same components that blow out at 16 pounds in the 3rd gens. You can find a lower pressure radiator cap and many have run one without issues.

 

I had the same issue with my 09 Explorer. I replaced the housing and the t-stat and it has been fine since. I always watch coolant and oil in this hot Texas summers.

 

Please disregard....I meant to post in the 7.3 section but was on the mobile site. I guess my screen was just low enough that it caught yalls thread instead

 

With my 2002 4.0 Sport Trac I learned that when you're going to replace a hose you need to replace ALL of them at the same time.

Recently I thought I had the dreaded thermostat housing leak, but turned out the by-pass hose under it had a pinhole leak which sprayed coolant everywhere. I still replaced the housing along with the hose. Soon after my radiator leaked. Got an all aluminum radiator, new pump, and the rest of the hoses that I hadn't replaced before. The Sport Trac had 170K miles on it and anything can give out at anytime so I didn't want to take anymore chances. New radiator came with a new cap, but it wasn't a Motorcraft part. I chucked it in the garbage after ordering a new RS-76 cap. All my leaks are gone although I still get wiffs of antifreeze odor coming from outside, but no signs of leakage anywhere.