Strange cooling issue

String-a-ling

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Joined
Apr 4, 2021
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Location
S-TX
Ok fellers I’ve got a real head scratcher here. I replaced the ENTIRE cooling system last summer with mostly OE parts and recommended aftermarket parts on this forum including G-05 coolant. I even burped air out of this thing a couple of days over a week and while it helped, this temp gauge still creeps up in drive-thrus, traffic etc… yet IR thermometer reads 185 on the thermostat housing. Which thermometer would you believe?

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I'd check with an OBD2 scanner to see what to computer thinks, could be a gauge issue. Also might replace the temp sender but that's probably not it. Did you do a chemical flush with thermocure or prestone?
 
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I'd check with an OBD2 scanner to see what to computer thinks, could be a gauge issue. Also might replace the temp sender but that's probably not it. Did you do a chemical flush with thermocure or prestone?

I didn’t have time to thermocure it while I was doing the replacements last year. All of the above will probably happen in the next few weeks.
 
I would put a manual gauge in it under the hood and compare the reading to the dash gauge, a old school test for the fan clutch is to stick a rolled up news paper in the fan after it gets up to operating temp then start the engine. You wont be able to keep the fan from turning if the clutch is ok.
 
Ok fellers I’ve got a real head scratcher here. I replaced the ENTIRE cooling system last summer with mostly OE parts and recommended aftermarket parts on this forum including G-05 coolant. I even burped air out of this thing a couple of days over a week and while it helped, this temp gauge still creeps up in drive-thrus, traffic etc… yet IR thermometer reads 185 on the thermostat housing. Which thermometer would you believe?

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Mine runs a bit over 210° all the time as do many others on this forum. As for the difference in the gauge & the temp at the thermostat, that’s sort of normal too. I retired from the ExxonMobil refinery in Beaumont, Texas & there were instruments there that cost several thousands of dollars that STILL needed to be zeroed & calibrated. My message is don’t put too much stock in any automotive instrumentation. It’s all actually pretty cheap stuff.
 
Mine runs a bit over 210° all the time as do many others on this forum. As for the difference in the gauge & the temp at the thermostat, that’s sort of normal too. I retired from the ExxonMobil refinery in Beaumont, Texas & there were instruments there that cost several thousands of dollars that STILL needed to be zeroed & calibrated. My message is don’t put too much stock in any automotive instrumentation. It’s all actually pretty cheap stuff.

It’s always run a dab over 210 during the summer months. It’s just been creeping up considerably higher lately in traffic and drive-through so it’s got me a little paranoid.
 
I would put a manual gauge in it under the hood and compare the reading to the dash gauge, a old school test for the fan clutch is to stick a rolled up news paper in the fan after it gets up to operating temp then start the engine. You wont be able to keep the fan from turning if the clutch is ok.

Not a bad idea. I’ll have to find one.
 
Run the gauge cluster test to verify the temp needle is not off. Push in and hold the trip odo button then turn the key to ON. Release trip odo button. The lights and gauges will run through a self test.

As stated earlier, get on OBD reader and read the temp straight from the computer.
 
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I also idle a bit over 210 displayed on the gauge when idling.

2 years ago I flushed the system with prestone cleaner/flush, replaced the radiator, thermostat, water pump with OE Mopar parts, all coolant hoses with gates and filled with G05. last year or this year I found the fan clutch had some slop and replaced it too with OE Mopar. nothing I have done has changed the idling temp creeping past 210 nor was I intending to fix any particular issue.
none of these components were acting up at the time of replacement and were replaced just to freshen up the system as OE parts were readily available still. My take off parts were placed in my parts storage for that one day when im too broke to buy new or cant source a part. ive seen no change in idling temp before or after. im not concerned about it but if I was the only thing left is to swap the temperature sensor... and even then Im still not concerned enough to do it.
 
According to my scan gauge, not too far past 210 on the gauge is more like 220-230.
 
I may have figured it out. The fan clutch has started making the same squeak @ 2800 rpm that the factory one did. Also seems loose when I hand turn it while the engine’s hot. I’m gonna rob my Mom’s low mileage TJ of its factory clutch for a day and see if it solves the creep up. Might have all been just the fan clutch in the first place.