Thermostat keeps going out. About once a year. WHY?

[Sparrow]

Hi. I have a 2000 eddie bauer 5.0. I am on my 4th thermostat in about 5 years. It went out last in Sep of 2010. I replaced it, and drained/hosed out my radiator and filled with new coolant. Now barely 6 months later by temp gauge is buried in COLD again. I'm buying the most expensive one Oreilly has (fail-open, lifetime warranty). Anyone have any ideas why this is happening? Thank God it's something easy to replace, but still very annoying.

 

[my98nnj]

Get a Motor craft t-stat and be done with it.

 

[Dan Whitaker]

Get a Motor craft t-stat and be done with it.

What he said.

I had the same problem with a Stant thermostat from O'reilly's. Once was enough for me. I went back to Motorcraft.

 

[Sparrow]

pulled the dead one and the fail-open button was popped out. Guy at oreilly said that happens alot, and usually when the coolant level falls a little low. I checked and I was about a half gallon low. Maybe if it's not a steady flow of coolant, it gets hit by a little bit of steam and gets too hot and POP? Not sure just guessing.

Also, he said that its not problem to exchange for a new one through the lifetime warranty, but if I want to save a trip to the store I can just push the button back in and reinstall it....that it's not actually broken...just "tripped". Guess as long as the gasket can be salvaged.