I just had (2) "Failsafe" thermostats stick in the open position within 3 weeks.
Temperature never even got hot! Was merely driving home, normal operating temperature, and all the sudden the temp gauge drops to around 100 degrees and stays there the rest of my drive home.

I pulled it out today to check, and sure enough it's locked open!

I bent the little brass tabs that lock it in the open position so that it can't actually lock open, and I put it back in until I can get a good high-flow one.

 

Wonder why it would "all of the sudden" drop to 100*?.....like one minute it's overheating and the
next minute it's not. Almost sounds like it "failed to open any" and then
decided to "max open and lock". Sounds like MotoRad may have some issues.

 

The fail safe motorad units look to me like they have this extremely over complicated design going on.

 

If the XJ overheated, I could understand why it would lock open.

Mine never overheated at all. It worked fine for about 3 weeks, then all the sudden went full open, and locked while I was driving home from work.

The one that I replaced 3 weeks ago was a Failsafe that did the same thing.
I put that one in around August when I put a new radiator in. Worked fine from August till 3 weeks ago when I was on my way to work, -2 degrees outside, and my XJ never got past 100 on the temp gauge..........Not much heat out of the heater. That was a cold drive to work that day..........Anyway, I "fixed" it so it can't lock open anymore..............
I'm ordering a Mr-Gasket #4365, and I'll replace it when it arrives......

 

Unless there is such a thing as clear glass pressure cooker, I guess it would be impossible to test a "fail safe" stat to see what the "locked open" temp is.

We've momentarily seen 230* on the ScanGauge and the factory idiot light never even flicked so my guess is 230* is not considered overheating. If that's the case, one would think the "fail safe" temp would be north of 230*, no? I believe the red zone (over heat) on the factory gauge is mathematically something like 241.25*. Wonder if MotoRad factors that in for their XJ replacement fail safe stat.?

 

What gauge temps were u seeing when it "worked fine"?

 

Well, I read this whole thread.

Looks like when I finally get around to redoing my T-stat housing again I'm going to slap in a motorad highflow.

 

The Mopar T-stats are not the high flow MotorRad. I just bought one and it appears to be the "premium" one with the jiggle valve. The high flow stat has three supports on the front, this one has two.

So after this whole thread, has anyone confirmed if this stat works alright? I tried it in boiling water and it seemed to work, but so did the Stant I have now which keeps my Jeep at 188-197 degrees.

 

Put it in and report back. It's all in the name of science and being a major contributor to the community.....

 

Wait, can we get funding for this?

 

No. But donations can be sent via PayPal to www.beerforcruiser.com.

 

That small brass plug in the flange is there to let air that is trapped in the engine out. There was a post about it on here some place. If the air can't get out you can overheat the engine after changing the thermostat. If you get a thermostat that does't have the hole, simple drill a 1/8" hole in the flange. When you install the thermostat make sure the hole is up.

 

....wait donations for cruiser when others (myself included) are buying and installing the stats??

Methinks that just ain't fair!

Serious note, I will be putting mine in at the latest Saturday.

 

Pretty sure it's a 1/16 hole.
Got mine today and plan to put it in come morning

 

1/8"