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Discussion Starter #1
I have a 2012 3500 6.7 with 334000 miles on her replaced the radiator, water pump, fan clutch, and the thermostat Problem is the temp fluctuations are 188 to 220 and never settle down constantly going up and down the road was flat and I drove it for 300 plus miles ?
 

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Most likely air still in the system. I'm not sure how to bleed it out. Hopefully someone will chime in with advice.
 

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Should be an air bleed on the passenger side by the ccv cover.
 

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And you could put the heater to full on, like it was done back in the day, although wasn’t really needed to do that.
 

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I have a 2012 3500 6.7 with 334000 miles on her replaced the radiator, water pump, fan clutch, and the thermostat Problem is the temp fluctuations are 188 to 220 and never settle down constantly going up and down the road was flat and I drove it for 300 plus miles ?
If you can get the plug out of the standpipe that is probably the best. If not remove a heater hose on the back of the valve cover and fill until coolant comes out. Re-connect the heater hose and continue to fill the system. Cycle the heater on and drive the truck to purge the air.

Just my $0.02
 

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Discussion Starter #6
I have a 2012 3500 6.7 with 334000 miles on her replaced the radiator, water pump, fan clutch, and the thermostat Problem is the temp fluctuations are 188 to 220 and never settle down constantly going up and down the road was flat and I drove it for 300 plus miles ?
 

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I have bleed the air out using the high plug till coolant came out? Then yesterday took it to town out side temp about 80 temp watched it go up to 247 then the light came on and defueling then got it up to about 45 mph and temp dropped to 180 and then climbed back up to 230 and stated the fast fluctuations up and down ? I’m stumped maybe temp sensor or the 3 new thermostat is bad again and it’s a Cummins thermostat from dodge ?
 

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Head gasket?

Sent from my SM-A102U using Tapatalk
 

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I have bleed the air out using the high plug till coolant came out? Then yesterday took it to town out side temp about 80 temp watched it go up to 247 then the light came on and defueling then got it up to about 45 mph and temp dropped to 180 and then climbed back up to 230 and stated the fast fluctuations up and down ? I’m stumped maybe temp sensor or the 3 new thermostat is bad again and it’s a Cummins thermostat from dodge ?
Defueling? Your deleted running a Mini Maxx?
 

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Discussion Starter #10
Yes all deleted H&S mini max 5 in straight pipe no muffler air intake egr delete no head studs but never run it in anything but mild
 

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Discussion Starter #11
I’m not saying head gasket as I’m not getting any thing into my coolant recovery tank no white smoke no milky oil and it does have a new radiator cap as well as the new radiator
 

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When you mentioned defuels, that got my attention.
High fuel/power settings don’t kill HGs.
Defuels and unmatched timing is the culprit. You don’t have to have milky oil for HG failure symptoms. Do you here your Cooling Fan run above 217f?
 
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So, your running defuels, and default timing?
 

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Discussion Starter #15
I understand that but there are no indication of a head gasket ie white smoke, milky oil, overflow filling up
 

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I would advise you to check the overflow reservoir when the truck is overheating. When it overheats pull off the road and immediately get out and raise the hood and look at the reservoir. If it is still between the cold and hot marks on the box you probably haven't lost the HG, but if it is completely full you will need to have the gasket replaced as well as possibly needing to have the head checked for a warp. I have a gut hunch your MM tune has caused your HG to fail. This is the very reason I had my 2011 retuned with an EZlynk tune after my truck lost the HG while running a Mini.
 

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Discussion Starter #20
I have a 2011 Laramie 3500 6.7 and I have EFI live tune in that one and that one did fill over flow tank so I put head studs and have the head shaved .05 to make sure it’s straight but this one doesn’t fill the over flow tank I’m leaning towards the coolant temp sensor ?
 
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