I was working on a Olds Intruge and think the thermostat has failed closed. So I went to Auto Zone and purchased a fail safe (open) one. I thought all thermostats were fail safe open for the past 10 years. Why would anyone or any car manufacturer install a $5 thermostat that can fail closed when a $11 thermostat would fail open?

Are the Whaler t-stats that we so proudly install in our 850's fail safe open?

 

This is pretty basic but I'll take a stab at it. I'm going to build 200,000 cars. I can save $5 on each car by using a good quality part that does the job needed and likely won't fail until it's long gone form my customer. I just saved myself 1 million dollars That's why.
Now I'm an auto manufacturer and I'm making millions of cars, what do you think I'm going to use ??

 

lol, very true... when it come to manufacturing, it all boils down to the bottom line and our friend statistical failure, otherwise known as "risk".

 

The fail safe thermostats are misleadingly labeled- They can and do in fact fail closed. The "pellet" fails, the wax leaks out, and it's all done. The "fail safe" ones are actually designed to fail and need replacement if there is any other cooling system problem. The water pump stops, or the fan quits, the engine starts overheating and the thermostat locks permanently into an open position. IMO, it's a poor design. If you're already overheating, locking the thermostat open won't help at all.

 

Well, I changed the dang thing, tool all of 15 minutes. The one that I took out looked like a fail safe one that was stuck CLOSED. Go figure. The car is still running a little warm. New water pump and now new thermostat. Runs between 211 and 228. Before it was going over 245 pretty quick. They claim 260 is the boil point for 50/50 mix unpressurized and 275 under pressure.

 

I don't have a reason for it but I'm not a big believer in the "fail safe" thermostats. For an 850 at least, the thermostat is easy enough to do and they are relatively cheap. I do a thermostat when I first get a car, that and every three to five years when you change out the coolant I do a thermostat. I do add a bottle of conditioner or "water pump lube" yearly to control rust and the solution getting too acidic. I just haven't had a problem with a thermostat yet.