1999 Explorer Leaking Antifreeze - solved

[Motolz]

I only drive my girl about 2000 miles a year... she has 200k+ and is all stock!!

For the past year or so, she has been leaking coolant but I could never find a puddle. Because I didn't drive it much, I would always just top it up after drives.

Well, I decided to get into it the other day and was going to start with the lower thermostat housing, which was going to be a pain.. When I removed the upper housing (original thermostat by the way), I noticed it was all chipped up on the inside and hence the source of my leak, which was going back on the block and evaporating before it could reach the ground. Luckily I didn't have to go any further!

Not sure what would have caused this.

Hope this helps others with this Mystery aliment! Photos attached.

 

[XLTrunner]

Yep...that thermostat housing design is so prone to leaking over time that it's automatically the first place to look when you notice a coolant leak. Amazing that yours lasted 200K miles! I once installed an aftermarket housing (Four Seasons) and it lasted 2 wks.

 

[donalds]

Buy a metal one and never mess with it again

4.0 SOHC Metal Thermostat Housing Comparison

eBay price (shipping incl) for Austek aluminum thermostat housing seems to have come down a bit. Also includes bolts, housing gasket, thermostat, t-stat O-ring, silicon bypass hose and hose clamps. Explorer Mountaineer 4.0L SOHC Thermostat Housing w/Sensors Hose/Clamps/Bolts | eBay

www.explorerforum.com