cruiser54

Scanning a Renix shows the same. Closed loop happens way before 195*. Usually a minute after start-up.

djb383

All I'm saying is, the statement above in bold is false, wrong, incorrect, misleading and keeps getting perpetuated on the Internet as such......and we all get it that u r happy with a 195. Peace out bro.

djb383

.......and this helps a bunch to dispel Internet/forum myths as well.

Saying that the coolant temp must reach 195F in order for the loop to "close", is just wrong.

wiggles

These are two COMPLETELY different things.. the temperature at which you'd scald yourself vs when a engine runs optimally is probably the worst reference of hot I've ever heard... no offense..

djb383

....and since the more important temp is about +/-650*, the operating temp of the O2 sensor, stat temps/coolant temps seem to be a moot point with regard to engine efficiency/performance on late model efi/computer controlled motors.

Firehawk068

I was merely stating that 160 degrees was damn hot............180, and 195 are even hotter.........

BlueRidgeMark

That's barking up the wrong tree. Fix the stat.

djb383

Can those goofy "fail safe" stats be unlocked? It would be interesting to see one tested in an oven to see at what temp it "fails open". I've always said a MotoRad "Fail Safe" stat is a gimmick.

Almost sounds like the OP has a overheat problem AND a now a underheat problem caused by a gimmick t-stat.

Firehawk068

The second one of mine that failed, I cut off the brass locking tabs that "Lock" it open, so that it wouldn't lock open............I put it back in until my
Mr Gasket/Robertshaw thermostat that I ordered, came in.............

The gimmick is that they claim to lock in the open position when the vehicle overheats.................The problem with them is that they lock open without the engine actually overheating............

Both of mine that did so, happened during normal operating temps (190-200 degrees)...............then all of a sudden, the engine temp dropped way below operating...............

cruiser54

Exactly.

djb383

Were both "failures" 195* stats? Is 190*-200* going by the dash gauge?

Firehawk068

Yes, both were 195*, and yes, by the dash gauge, they both failed/locked open at normal operating temperature
(I have verified my dash gauge against the computer temp sensor by watching live sensor data with a scanner. The dash gauge is accurate within 4-5 degrees. Could also be a variance between the front of the engine, and the rear of the engine, where the two sensors are mounted?)

My thought was that possibly, at certain engine loads/rpms, or possibly when suddenly letting off the throttle after acceleration, the 4.0 cooling system might see greater than operating temperature at the thermostat for an instant, causing the overtravel of the thermostat?
Also could be thermostat placement in the 4.0 engine? The copper (slug) housing the wax that actuates the thermostat, might sit too close to the #1 cylinder combustion chamber, causing it to get higher than operating temperature?

Firestorm500

Well, maybe. My "Failsafe" locked open at a normal temp, causing Jeep to run very cold. No heat.

The takeaway here is to just stay away from them.

djb383

Wow!......a 195 stat "fails safe" at 200. Impressive MotoRad. I'll stick with Stant as I've never had an issue with them.

cruiser54

Try a factory stat you stubborn old fart. LOL.