It's exposed to boilng water temperatures as I stated earlier. It is, in fact, exposed to temperatures at 260* or so in a relatively extreme overheating situation as you mentioned. But it doesn't ruin it.

On your stove, you cannot exceed 212*F on the thermostat in an open pot. Won't hurt it.

 

Water in a pot on the stove won't get hotter than 212. An automotive thermostat in boiling water in a pot on the stove will not be harmed in any way shape or form...

 

...if it does, the stat was defective to start with and you don't want it in your block.

 

The stat is not in the block. Quit argueing and test the stat. What u need to know about the stat occurs well before 212F.

 

Here is the thermostat...in the block. You are the one arguing, amigo, and losing because you are mistaken.. Long block... :P

 

I am not trying to be a jerk here. There will be occasions where the stat does not open at 190 and may not open at all. That would be another failure of the part in the test. Since there is a bit of 'give' to these, where they may open at 195 or 193 or whatever, one might need to go all the way to 212 to check to see if the thing will open at all. If it doesn't open at 212, get a new one. If it opens at 195, it would probably be fine.

Personally, I think 190 is a bit too warm. That the 4.0 commonly runs at 210 kind of makes me nervous. Blown head gaskets suck, and cracked heads and blocks even more...

 

The stat is in the head....not the block. If u have a 190F stat , u have some kind of oddball after market stat. Pull it, inspect it , test it IF it is closed. A good stat should start to open within 2-3* of it's rated temp. It should be wide open +/-15* above it's rated temp.....if not, replace it.

210F is going by your goofy factory dash gauge. Why would ACTUAL temp be 210 when using a 195F stat?......especially in cool/cold weather running the heater.

 

subscribed

 

http://www.jeepforum.com/forum/f11/t...ature-1221092/

I was mistaken. The stock stat was set for 195'.

Yes. The OP should test his thermostat if it is not stuck open when they pull it out of the block...the long block.

How should they test the thermostat? Put a pot of water onthe stove and put a thermometer that goes to over 212' in the water along with the stat tobe tested. Turn on the heat. Note the temp on the thermometer when it starts to open.

If the stat is bad and won't open, they would know when it didn't open when the water was boiling at 212.

212' water won't hurt the stat a bit. It was made to work in those conditions... the 4.0 commonly operates at 210' as verified by pretty much everybody who owns one. The thermostat does not regulate this, it merely keeps the coolant inside the block until it is up to operating temperature. This helps the engine get up to temp faster.

This situation is not the issue with the OP, but others will read these threads and they may find it useful to learn how to test these things.

 

That link is just someone's opinion on another Jeep forum.......it contains mostly myths, few facts.

 

JeepForum.com is rife with myth and not facts? I like this forum better, but jeepforum is pretty good too. Many of the same members talk on both.

How would you test a thermostat? I am curious because I learned the pot-on-the-stove method many years ago from a service book. It is tried and true and has been used since automotive thermostats were invented. It is pretty simple and not much room for mythology...

Maybe we can shake hands and just call it a difference in semantics between Texas and Arizona?

 

Nowhere in the FSM does it say anything about, or reference to, 210F coolant temp being stock or normal coolant temp. The only thing that says anything about 210F is that goofy factory dash gauge and factory gauges r known for inaccuracy.

I've post numerous times that the t-stat is the ONLY cooling system component that can be easily/effectively tested so here's goes again.

Completely submerge the stat in a pan of water, bring temp up while watching the cooking thermometer. The stat should appear closed or only slightly open at it's rated temp. It should be wide open (+/-1/4") at +/-15* above it's rated temp. It should open/close very slowly and very smoothly in an infinite number of positions (hover) between closed/open.

Here's a 180* stat being tested. It can clearly be seen that it's closed, or very close to closed at it's 180* rated temp and wide open at 195*.

 

Wide open, +15' over rated OEM temp of 195 = 210'. 2 degrees shy of boiling water. There is an acceptable range of +/- to work with, making it perfectly possible that boiling the thermostat while testing is probable.

Boiling a thermostat at 212' is not going to harm it one bit, as it is designed to operate well into the 250+ range while submersed in liquid that is half water.

 

In the time it has taken to elaborate on this idea, I could have removed and replaced my thermostat 2 or 3 times. The inline 4.0 puts that thing right in your face as soon as you pop the hood. 3 bolts and it is out. Ideally, you would have a new gasket for the neck, but RTV works fine too...

I hope the OP isn't freaked out too much by all this banter, cus it is much more easy to troubleshoot this part than it would seem amidst all the bickering...

 

In boiling water, the stat is exposed to air (thousands of bubbles). That condition (boiling) does not exist inside the motor, even at 250*. U r saying it can withstand the exposure of high temps is ok......I'm saying, exposing it to air is not ok. Again, don't toss a stat into boiling water......doing so tells u virtually nothing.