2002 Discovery with 103,000 miles.

So, my thermostat housing has slowly been leaking coolant from the top hose for a while and i have just topped off the coolant as necessary. I finally got around to replacing the thermostat and housing and when i pulled off the top hose i found this (see pics below). The nipple where the top hose attaches is completely corroded away. Also the housing is very brownish in color as if burned. I dont have overheating problems and the thermostat has always worked fine except for the leak. The problem is fixed, but does anyone know what caused it to corrode so badly? Was it just time or something more sinister?

 

How often do you change your coolant? Do you have an internal leak somewhere? I would test the pH of your coolant just to be sure. This does not bode well for your gaskets.

 

http://sancarlosradiator.com/dex-cool.htm

Yet people still dont believe me why I say DUMP THE DEXCOOL!!!!
The corrosion is from your coolant, DII's came from the factory with DexCool.
Now, imagine what the rest of your cooling system look like.

 

I flushed the Dexcool around 95,000 miles and have since been using Peak 50/50...so hopefully i caught it just in time.

 

DexCool needs to be changed every 45,000 miles or 36 months, whichever is sooner.

 

All coolants, for our engines should be changed every 30,000 to help keep out engines from turning into toast.
Do you have the old style bleeder screw, located in the upper hose or the new style, located in the black tee? If you have the old style change it out before it blows, cause they do fail.

 

Pretty sure i have the "old style"...i will get on that asap. thanks for the help!