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Discussion Starter · #1 ·
So it has been cold in the 20s and 30s the last few mornings and jeep does not warm up above 140 degrees in the morning this is an hour long drive as this is my daily driver. But when I get off at 2 pm and its 50 out the temp will get to 190. I believe I have a screwed up fail safe T-stat.
 

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Jeeps don't seem to Like Fail Safe Thermostats.
I'm not disagreeing with you, I'm just curious what you're basing that on. I don't know either way but if there's a reason for that it would be good to know. A fail-safe thermostat seems like a good idea since one would have saved me about 6 months ago when my non-failsafe thermostat stuck in the closed position and my engine was overheating. I had to remove it and make a new gasket out of a cardboard box while on the trail when it started overheating so bad I could no longer drive it.
 

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I'm not disagreeing with you, I'm just curious what you're basing that on. I don't know either way but if there's a reason for that it would be good to know. A fail-safe thermostat seems like a good idea since one would have saved me about 6 months ago when my non-failsafe thermostat stuck in the closed position and my engine was overheating. I had to remove it and make a new gasket out of a cardboard box while on the trail when it started overheating so bad I could no longer drive it.
for some reason they don't work on 4.0L's. they always lock open shortly after install.

examples:
Warning on Fail-Safe thermostat - JeepForum.com
Anyone use O'rielly fail safe thermostats? having issues and thinking bout switchin - JeepForum.com
 

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I don't understand the concept of the fail-safe mechanism. It seems like, in order for the fail-safe mechanism to function, the thermostat first has to overextend in the open position, at which point it is locked open permantly. It does that when any significant overheat condition occurs, whether the thermostat was at fault or not.
 

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I put one into a chevy truck thinking it would be a good idea, until I had to take it out about a day later and do it all over again. Not learning from my first experience I put one into my jeep when I first got it, same result as my chevy except it "failed" as soon as my temperature came up to normal operating temp. They are junk, I will never use one in any vehicle again.
 

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Discussion Starter · #8 ·
It's a good concept keeps you from overheating the engine so far.
So now I'm on my way home and now it's up to normal operating temp but in the morning it won't get there
 

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Thermostat stuck

I have been fortunate in 57 years of driving mostly high mileage vehicles to never have had a thermostat stick closed.

The 4 banger can about get by with just the heater as a radiator in cold weather. Can certainly do it when idling.

I would put in the best quality standard thermostat I could get, and then buy and put another, along with the tools, in my spare case if I were worried about it. Or just put in an extra gasket so it could be reassembled sans thermostat.
 

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Not certain of the Reasons Jerry. From my own experiance and from doing some research it seams to be an abnormal amount of failure with the Failsafes and Jeeps. I can't tell you what years or models, just seems that many have had problems. I ran one in my Old Dodge Power Wagon and never had a bit of problem for almost 100,000 miles. :confused:
 

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I agree with the RobertShaw 195. Now if Quadratec ever gets them off backorder I will be happy to tell you how they work. If you have a really gung-ho fan you could be pulling too much air when it's cold. Or, as someone suggested, your thermostat has gone south. Try partially blocking your radiator with a piece of cardboard. That should be enough to bring your coolant temperature up. And if 50 is your expected high it shouldn't overheat during the day, but keep an eye on your temp gauge. I'd say "yeah, get the RobertShaw" but the way it's going I don't expect to see mine till spring...
 

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There are a bunch of places besides qtec to get RS thermos, I have seen a few but the ones I saw want like $10 in shipping, they seem to have them in stock though!
 

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When the temps here dropped into the 10s and 20s, I noticed my engine would never fully heat up. I pulled the t-stat and tossed it into a pot of boiling water, along with a brand new one. Sure enough, the new one opened much *later* than the old one - but both were 195F units.

I recommend just replacing it with a regular unit from the auto store. If you're worried about it "sticking", keep a spare in the back. Problem solved.
 

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Well I learned something in this thread, I sure won't be using a failsafe thermostat. It sounds good but...
 
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