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Temp fluctuation

98whitelightnin
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98whitelightnin

98whitelightnin

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I know alot of folks have temp fluctuation but I think it usually swings low instead of high. I had this trouble a few months ago and fixed it with a new water pump but its back again. I just had the radiator cleaned and rodded but it hardly had anything in it. Its got another new water pump and I have ran two different radiator caps. I have 3 different t-stats and they all fluctuate the same, two are 190 from napa and one is a cummins 180. I generally see swings from 190-203 or so, usually cruising it stays around 190-194 but will jump up to 197-199 for a second then back down. That doesent bother me as im reading those temps from the ultra-gauge and I think those are fine but when im getting on the interstate or accelerating it gets up to 203 or so and stays there for a few seconds on both the ultra-gauge and the dash gauge. I took it to the radiator guy yesterday and he put some kind of tester on it that is supposed to change colors if there is carbon dioxide present and it didnt change so im hoping its not the headgasket. When I come to a stop or so it goes back to 190 and pretty much stays there or gets cooler so i dont think its the fan clutch. Also after it idles for 10 minutes or so and I turn it off the fan clutch will spin for a few seconds after I turn the engine off but if I get off the highway and let the egts cool to 300 then turn the engine off the fan will stop just about as fast as the motor. I dont think I could put any kind of loaded trailer on this truck or it would probably overheat. Im lost here and just shy of pulling the head.:banghead:

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98whitelightnin

98whitelightnin

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Shot a couple videos earlier, they are shacky but my truck rides like a wagon. The temp is on the left side in the middle, its a little hard to make out but you can see the fluctuation during normal cruising and acceleration. Put a heat gun on the t-stat housing yesterday and it read 178 while the ultra-gauge said 182. I ordered a new temp sensor from geno's earlier, dont think it will change anything but for less than $10 I figured I would try it.

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ISX

ISX

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I would check the connection on the ECT sensor. I have a digital gauge with it's own temp probe that I stuck in the back of the head (stock ECT placement on 12V's) and it will never instantly change temps like that. When my thermostat opens initially, it drops off a degree every few seconds, it is by no means instant. Definitely not the instant drop to 150F like I had happening years ago. My oil pressure gauge has a bad connection on the probe itself and the oil pressure gauge kinda flutters as the wire shakes.Just saw your vid and yeah that thing was going from 188 to 194 every second..that's just not gonna happen like that. I'm putting my money on the ECT sensor/connection.

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98whitelightnin

98whitelightnin

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Ya, the ultra-gauge updates every 2 seconds I think. My ect plug got broke some years ago and I got another and wired it up but couldnt remember if I soldered it or not so I pulled it apart today. When I did, one of the wires pulled right out but the other was still intact and I did solder them but im not very good at it so I cut the old solder off and re did them today as good as I could. i am anal about things and its been driving me nutts, not the 188-194 swings but the 190-203 swings seems like to much to me. If it did it before I probably wouldnt think about it but I dont think it did. Blast that ultra-gauge for showing me these things.:ahhh:

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Rogan

Rogan

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I sure will, is it under the hood?

- - - Updated - - -

Mike, do you how fast the scangauge updates? I think this ultra-gauge does it every 2 seconds.

I'm in agreement with others; that temp moves around WAY too fast to be actual coolant temps.. 5-15* swings within seconds just ain't happening, legitimately.

Fuse should be under the hood, in the PDM box (driver's side.) 140A fuse, IIRC..

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Mopar1973Man

Mopar1973Man

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Rogan right. In the PDC box there is a fuse near the heavy red and black wires that has a fuse held by two phillips screws. Just remove the screw and take a ride and see if it calms down if it does settle down you now a candidate for the TQ Conv lock up thread... :whistle:http://forum.mopar1973man.com/threads/5937-Torque-Converter-Lock-Unlock-Issues

Mike, do you how fast the scangauge updates?

About 2 seconds as well...
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Mopar1973Man

Mopar1973Man

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Hmmm... I was hoping was was AC noise. Dang! :banghead:As for head gasket leak if you has a small one it would build coolant pressure near instantly. Or have excessive blow by and oil loss... Unless its leaking between cylinders then the only way to see it would be a compression test.Also checking my lowest coolant temp as for coasting long distance down hill it will cool down to 184-186*F and sit till the EGT's rise again...I still say there is something wrong there with the sensor / wiring it should jump that fast. As for my truck it takes nearly 3 miles to go from 195*F to 205*F on a 7% grade.

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98whitelightnin

98whitelightnin

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I did buy a new radiator cap but it flucuates so put the old one back on. I let the 15psi cap go with the 03 I sold because I was fighting another issue then but turned out it was some wiring. Im off tomorrow and if we dont get flooded out im gonna get another t-stat and maybe fan clutch.

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JOHNFAK

JOHNFAK

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New temp sensor didnt help, actually seemed to move more. Im gonna replace the t-stat tomorrow and if that doesnt do anything I will start saving for a headgasket and studs. What all needs to be done to the head when I pull it off?

Depends if its just to replace head. else Studs Port job if you can afford it. Its the time to do it. Magnuflux and check of head for cracks and decked if required. Gasket Clean block with razor etc Tap the stud holes since you have head off. :think: 1 question tho - what happens if you do all that and its not the head - are you going to be bumbed ?? :shrug:
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