I put one in on my daughter truck last year when her old thermostat went out and I put one on my old truck this year.

Within a month my truck was always running cold and heater wouldn't get warm. Noticed it the most when I was wanting to get the truck warm on a 48° raining day to warm my son up after he had been siting in a 3 hour steady to down poor deer hunting and it never got warm.

I came up with the new fail safe thermostat was stuck open. It was basically new.

Last night and this morning I took and picked up my daughter to and from work since it had snowed. I noticed her truck never got over 110° and heater was not heating. I suspect its the same issue. Has coolant in the radiator none in the over flow. going to wait for it to warm up some single digits are not fun for me to work on her truck.

I have always had good luck with failsafe thermostats up tell now. Im not spending the extra cash on them anymore. Then again I guess its better than getting stuck on the side of the road over heating when they get stuck closed and they have done what they are designed to do. Maybe they just don't Last as long as they used to like about everything these days.

Though this may help someone having similar issues with trouble shooting.

You must have some terrible, awful, bad luck with thermostats. I believe that it’s been 50 years, no exaggeration, since I had to change a thermostat.

Kind of reinforces they don't Last like they used to. Then again most people are not driving 28 and 29 year old trucks and things break and wear out. It's expected. But I have never had thermostats fail this quickly or had any problem with fail safe.

I did have trouble with bad alternator for my 01 Ford excursion with 7.3. Had to go through 3 before I got a good one. Changed one on the parts store parking lot jumped it to have juice to get it to start. It left me sitting at the light a block away. Had the new one tested it was bad. The next lasted 2 weeks. The third has lasted several years . Bad new parts happen. It's frustrating when it does for sure.

There should always be some coolant in the overflow.At least in everything I've ever owned. Make sure your radiator and overflow are up to level. Overflow usually has a level mark on it. Never heard of failsafe thermostats. Just buy whatever cheap one it calls for and the parts store has. Wish you luck on the next one

my 01 E350 was the same 3rd alternator was the one that ran the next 15 years till I let the van go

the 2000 expedition I put 2 themrostats in and neither one was long before it was open too much

I took to just putting carboard over the grill when it was cold that kept the heat in a bit more and everything would warm up

I run cardboard over my radiator 24/7/365

Fail safe just stay open when they fail insted of getting stuck closed. Won't cause you to over heating and end uo stuck on the side of the road. They cost more but are still cheap. I think around $25 or $30. I always saw it as cheap insurance. But have not had them fail this often tell now. Maybe they are still worth the extra expense if the standard ones fail at the same rate these days? I mean I didn't get stuck on the side of the road after all. But buying things that have failed again seems like a poor choice.

I May not get to it today I forgot about my eye doctor appointment taking a chunk out my afternoon

You didnt put them in upside down?

I've heard of people drilling a small hole in the thermostat to prevent problems. YouTube it. I've never done and not recommending it though. Just sayin.

The fail safe thermostats are notorious for sticking open sometimes the first time they open they stick. In the shop I work at we will not install one because we have had almost everyone come back stuck wide open and have to warranty every one.

Just got to it today. It's definitely stuck opens. I'm waiting on it to warm up and check for leaks now. Probably should have replaced the thermostat housing it had some corrosion on it but I didn't want to take the hour plus to go get one. I have picture of the new one closed and old open i wanted to post but this new phone won't work posting like my old one.

The front hole the bolt that hold the housing down part of the cast lt on the motor side is broken off so have a smaller bolt with nut holding it down. Makes a simple job just a bit more of a pain getting the nut off and on. Lost a 10mm crows foot to the engine compartment. Bought some swivel head ratchet wrench after that. A piece of electric tape keep the nut from falling through. Worked out well.