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Unread 11-14-2013, 01:30 PM   #1
leftfield6
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Do I need a new thermostat? (5.9L)

So, cooler weather is upon us, and I realize my 5.9Limited takes quite a while to make some dang heat.

Think I may need a new thermostat. This pic shows where my temp gauge sits after about an hour of interstate driving. Sorry for the fuzzy, but I'm snapping a damn pic at 70MPH, as you can see.



That's too low isn't it? Ambient temp that day was mid-50s or so.

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Unread 11-14-2013, 01:41 PM   #2
RWC
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Could be a bad sending unit too.
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Unread 11-14-2013, 02:37 PM   #3
StPaul59
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Almost looks like you have a 180 stat in there.
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Unread 11-14-2013, 03:27 PM   #4
riot1987
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Could be a thermo. Pull it out, put it in some boiling water and check to see if its opening up or not. Get a 195* one if you decide to replace it
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Unread 11-14-2013, 04:46 PM   #5
pageman
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the old boil test is ok but if you went through the trouble of taking it out just replace it since its a whole 7 bucks.mine drives at that temp all the time too so your not alone
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Unread 11-14-2013, 04:51 PM   #6
PolkaPower
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Looks like it's stuck open. That happened to me when I was using a POS Failsafe. I replaced it with a stock Mopar T stat. The difference in quality when the two are side by side is obvious.
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Unread 11-14-2013, 06:04 PM   #7
leftfield6
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Yeah, I think that's the weekend project. Just replacing it. I'm going to the dealer to get an OEM one, too many bad units from the FLAPs
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Unread 11-14-2013, 06:44 PM   #8
Gearhead31
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mine isn't wanting to get above ~130º, gonna replace mine tomorrow morning.. Not sure if you have a 180º therm, yours is shot or if it's something else. If you're willing to put in about $10-12 for quality parts and half an hr of work, go ahead and replace it. With that little cost, it wouldn't be much of a loss if it turns out it's something else and it gives you a definitive answer. Be sure to have two gallons of antifreeze to throw into it afterwards though!
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Unread 11-14-2013, 06:55 PM   #9
steve_up
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Flush your heater core as well if possible. I second replacing the tstat, they're cheap and fail.
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Unread 11-15-2013, 05:42 PM   #10
leftfield6
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Okay, it was the thermostat. I went by the Mopar dealer, picked up an OEM thermostat for about $15 with gasket. Super easy R&R. Lost about a 1/2 gallon of coolant, most of which somehow managed to miss the basin I had placed underneath. Kitty litter took care of that. Don't have a cat, but I do have old vehicles, so kitty litter is always in the garage.

Replaced coolant, fired her up and went for a drive. Gauge moved up MUCH faster than before. I had heat coming from the vents in about half the time, a marked improvement from before. Gauge reached what looks like 190* to 200* and stayed right there.

About 20 bucks and about 45 minutes, some of which was spillage clean-up. GTG.

Thanks all.
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Unread 11-15-2013, 08:43 PM   #11
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Glad you got it fixed!
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