I have a 2006 V6 mustang. I just replaced my radiator and the upper and lower hoses in hopes of fixing a leak. BUT! IT IS STILL LEAKING!! I was checking for leaks and didn't find any in the hoses or reservoir or anything like that. Instead I find it dripping from a bolt on the lower left side of the engine block. Not sure if this is the DIRECT leak or if it is just the residue of a leak coming from higher up. Any ideas of what I can start checking for? I don't want to take it to a shop just yet.

 

Check the t-stat housing. They are known for chronic leaking on the V6. Thank ford for making them out of plastic.

 

To check that out, is it just a visible check like looking for cracks?

 

See if you can find it first. Then clean it up and drive it for a day or two. Check again to see if it's leaking. I feel like a visible crack would be alot more obvious than a drip.

 

This is what it usually looks like - on the back side so you can't see it until you pull the housing. And it will often cause the "leak" that looks like what you have seen on your car.



It's easy to replace if you are stock - not so easy if you have the Xcharger like I had on my car. Had to remove the blower to get to one of the bolts because it is trapped underneath it. But the replacing of the housing is about a half hour job.

 

Thanks for posting those pics, Jim. Even though my wife has an '06 V6, I've YET to take notice of her t-stat housing despite all the posts about the issue. A spare is on my list...

 

It just seems to be luck of the draw for the housing failing. Mine went 199,800 miles before it failed. Others have replaced it multiple times on far fewer miles.

 

Any time you have a coolant leak on the early S197's, the plastic thermostat housing should be the first thing you check. The engineer that came up with the bright idea to make them out of plastic has, hopefully, found a new job as a Walmart greeter. I'm sorry to hear that you went to the expense of a new radiator and hoses when the replacement part for the likely culprit is usually under $50.

 

Yep having a plastic thermostat housing is not the brightest idea, especially being right next to a hot engine.
I just replaced out my thermostat housing this past weekend. It had been leaking from the backside for over a year. Due to the leak being towards the back of the thermostat housing, most of the coolant went inside the "V" middle section of the engine. It has been puddling up for over a year and was not easy to clean out. The remaining coolant will need to burn off from the heat of the engine.
FYI, This is a very common problem with the 4.0 engines on the Mustangs, Explorers and Escapes.
Look for leaking coolant behind/below the throttle body area.
I purchased the thermostat kit from autozone. It includes the upper/lower housings/thermostat/O-ring/seal.
I also had to purchase a new thermostat sensor, due to the old one not fitting. The old one, the seal was worn out and too flat. It was too loose and would not fit properly in the new thermostat housing. I went ahead and purchased new coolant to do a coolant flush, purchased new throttle body gasket, since we had to remove the throttle body.
I have a thread on the 2005-2013 section if you want to read.

 

Hey Scotty104, I am seeing the exact same leak. It is dripping from a bolt with a heater cable bracket on it. Noticed it after replacing the water pump. Did you find the problem? The bolt is attached to what looks like the engine mount and the bracket is holding the heater hose that comes off the water pump. I have checked to see if it is runoff from some other place and the answer is no. I have been searching this forum for hours until I found your Q and it looks incomplete. Everybody is hung up on the thermostat housing.