I'm still curious as to when (what temp) a MotoRad "FailSafe" t-stat is designed to fail/lock open. Do all 3 (160, 180, and 195) have the same "FailSafe" temp or do they have 3 different "FailSafe" temps???? Guess that's the $64K question.

 

No I never did. Now that it has warmed up I can see the stat functioning normally on the temp gauge again and the heat is back to full strength as well.
It appears my specific XJ just does not like very low temps.

 

I wondered that myself.
Both of mine failed at (what I thought were) normal operating temps........

Maybe I'll have to "Obtain" the 3 of them and do a temp test..........

 

It's not winter for another 3+ weeks......things just don't fix themselves. Next round of bitter cold weather may be just around the corner. A properly functioning 195 stat, even in single digit ambient, should quickly run coolant temp well north of 150. For your new son's sake (and mama's), check things out.

 

GO FOR IT! A t-stat/coolant temp thread is as good, maybe better, than any old oil thread. LOL

 

Let's say your fan clutch was bad (ran locked all the time) could this cause a cooler running temp? I understand they work off of temp on how they "lock"....just curious. Mine doesn't heat up to correct temp in low temp weather (runs about 170-180*F) but I still have ample amounts of heat for the cab.

 

Minimum temp should be very close to the stat temp rating, even if the fan is locked. If the fan is locked, it's going to reduce fuel MPG, reduce power to the wheels and make constant noise.

 

Wasn't sure. I always figured the temp was controlled with the fan clutch. Kind of a metering device so to speak.

 

Thats normal for single digit outside temps..................
Mine runs in that range when it gets that cold out.

 

I agree. That sounds normal.

 

I ran mine locked (just move the thermal coil in the center) for most of a winter, other than noise and perhaps fuel mileage, no real difference.

 

So..........there r some XJs out there that don't run 210 year round????......where they were designed to run. Really? LOL

 

1/3 of engine heat is lost to the surrounding air by radiational cooling. At highway speeds in sub-freezing weather, the 4.0 does not always produce enough heat to stay at or near 210*.

Slow down or just do the stop and go driving in town, then it will warm up.

I have personally experienced this on both my XJs. And their thermostats are MOPAR 195* that function properly.