SLVRSTNG06

So last week I got a check engine light saying that the engine wasn't hitting operating temp- noticed i was losing coolant also so i changed the thermostat, thermostat housing, and coolant sensor and did a coolant flush- drove the car 300 miles yesterday and noticed the car leaked coolant again over night. I'm at a loss as to what to do now- any input guys?

Nuke

Did you use the Ford plastic t-stat housing again? Be sure that the gasket is installed properly and hopefully you didn't over-torque the bolts. There are a number of locations that you could have a leak so the hunt is on!

A pressure test may be in order.

kevinmalec

I feel your pain!!!! I also replaced out my thermostat housing about 6 months ago and the coolant is still leaking in the "V" of the engine. It looks like the leak is coming from the freeze plug, which is located in the "V" of engine, behind the thermostat housing. Supposedly the freeze plug can get corroded and start to push out, hence allowing the coolant to leak out when at temperature.Take a look there.
I did a cold pressure test a couple of weeks ago and it barely lost any pressure and did not leak. I am planning on doing a warm pressure test this Sunday to confirm.
I will update once I found out more...... :/

petrock

Yes, this is true. But they don’t push out. They rust from the inside out since they are (typically) made of steal. It starts as a pin whole leak and eventually gets larger and larger. If it is a freeze plug leaking you might as well replace them all because if one is rusted then chances are others are too. You don’t want to spend the time/money/energy replacing one only to have to do it again 6 months down the road.

I replaced the freeze plugs in my wifey’s 3.8L earlier this year. The plug behind the passenger side motor mount was rusted pretty bad and leaking like a sieve. That is what got me started on the job. I replaced them all and in the process found two more that had pin whole leaks in them that I didn’t even know about. I replaced them with brass freeze plugs so they won’t corrode like the stockers did.

kevinmalec

Well, after my neighbor (ex mechanic) did a warm pressure test on my Mustang, it turns out it is an external head gasket leak. It is slow and leaking out into the valley of the engine, therefore no internal engine issues will occur. Unfortunately, the issue will continue to get worse overtime and start leaking more, however as long as the leak is slow, I don't have to get it fixed immediately.