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This thread is very timely for me. I have a '16 JKUR I added HOAT to some time ago. I bought the coolant at a Jeep dealership, but some information must have been lost in the purchase process and I ended up with HOAT which I proceeded to use to top off my reservoir. It's now a year and half later and I'm just becoming aware of the different coolants!

So I'm all set up to do a drain/flush, but am stuck at step #3 - "Open the petcock.". The damn thing was impossible to turn with my hand! So, I got a pair of pliers and once it was knocked loose it was pretty easy to turn 1/4 turn (counterclockwise), but nothing was coming out. So I went ahead and turned it another 1/4 turn and still nothing. So...I turned it another 1/2 turn and still nothing! I went one more full turn and I still nothing was coming out. So I turned it back the two full turns and it didn't stop there. It appears to just be free spinning now, but nothing is coming out.

Any thoughts?
 

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Just seeing this thread, I posted over in the general forum. I've got a 2012, did a garden hose flush using a prestone flush n fill kit via the tube that heads into the heater core. Purged with low pressure air, then tried filling the system with distilled water as I want to flush the impurities (I'll do this twice before finishing with coolant). I am only able to get 8 quarts distilled water in the system including the overflow tank. My jeep calls for 10.5q. So anyone figure out what's with the large discrepancies???
 

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This was on my list to pay someone to do because when I did it on my 98 Cherokee it didn't go very well. I don't have heat in it now and the temp still rises a bit too high in summer.

I'll re-read and re-read and give it a shot on the Wrangler.

Thanks for the tutorial
 

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Just seeing this thread, I posted over in the general forum. I've got a 2012, did a garden hose flush using a prestone flush n fill kit via the tube that heads into the heater core. Purged with low pressure air, then tried filling the system with distilled water as I want to flush the impurities (I'll do this twice before finishing with coolant). I am only able to get 8 quarts distilled water in the system including the overflow tank. My jeep calls for 10.5q. So anyone figure out what's with the large discrepancies???
Same here, only 8 qt. I have no idea why. But my engine's running just fine, so I'm not too worried about it.
As long as you run the engine long enough with distilled water (like 20 minutes each time) you should pick up any pocket of old coolant that doesn't completely flush out...
 

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Same here, only 8 qt. I have no idea why. But my engine's running just fine, so I'm not too worried about it.
As long as you run the engine long enough with distilled water (like 20 minutes each time) you should pick up any pocket of old coolant that doesn't completely flush out...

I'm going to proceed believing you. But I can't find anywhere else on the interweb that says their jeep only holds 8quarts... :-/. No knock on you, I just like confirmation.
 

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I'm going to proceed believing you. But I can't find anywhere else on the interweb that says their jeep only holds 8quarts... :-/. No knock on you, I just like confirmation.
Might be worth asking a mechanic at the dealership.
 

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On the 3.8L the lower hose is halfway up the side of the radiator. The only way to actually drain it is via the (PITA) radiator petcock and the block drains, which are covered up by the motor mounts and dipstick tube. Removing the heater hoses at the water pump will help drain the heater core, but if you can't get the block drains open that's where you miss the 2.5 quarts everyone scratches their heads over. If someone knows a way to get those drains out of the block let us know.
 

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in your picture showing the two heater core hoses your arrows are actually reversed flow wise (on my Jeep) the left aluminum pipe flows into the heater core, and the right side with the odd bend flows to the engine just an FYI, not sure if that was changed in subsequent years after my Jeep was born, but thought I should point this out for others just in case.


other wise good write up and great easy to follow steps!! I probably need to do this to my jeep soon, I am currently using green coolant
 

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Is there a write up like this anywhere on the 3.8 liter engine?


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Is there a write up like this anywhere on the 3.8 liter engine?


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None I know of. Draining the radiator and dumping the overflow only removes about a gallon of coolant, leaving around 8 quarts still in the system. The block drains are blocked by the motor mounts and dipstick tube. You can remove the latter on the driver side with some fiddling and cursing.

Not all that crazy about his practice of blowing compressed air through the heater core.
 

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P0128code finally popped up on my Jeep 2013 Sahara. I had the cooling system flushed as well as the heater core back flushed . They flushed the block changed thermostat and ECT. Should have done this earlier now I actually have heat when I need it in the Jeep. 6 years and 120K engine is working great. I did lose horsepower as well on the highway when check engine light came on. I’m not sure if this is a safe mode off the pcm to ensure you don’t overheat. Local shop does my work did not go with the standard HOAT used dexcool by Prestone instead. Everyone gets wrapped around what to use. Jeep runs better than when it was new.


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Final 1/2 qt pocket of air out but lifting front 6-8 inches

Thanks for the instructions!
I had a check engine light and showed P 128.
Thermostat was replaced.
I first used 50/50 vinegar/distilled water to flush but then decided to use the Blue Devil flush. I also did 2 to 3 flushed with distilled water.
I also flushed the heater core as the instructions in this thread.
My system was pretty clean from the get go but I had considered changing from HOAT to AOT and I really did not know what was the coolant my used jeep had. I ended up using MOPAR HOAT.
Final fluid mixes were total of 9 quarts, 4 quarts of HOAT.
The over flow tank min level is 1 qt, and the max level is an additional 1/2 qt.
My final over flow tank level is just a tad below the max level.
I appears my engine temperature (at 55 mph, 6th gear, 77 deg F ambient, no AC/HEATER, is 203 deg F ( 125 deg F delta). Thermostat is opening at 195-196 deg F.

Next is replacing the radiator cap b/c the rubber is a little peeled of but still functions. Only difference is current one is set for 18 psia, and the new on is 17 psia.
 

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Had 128 code, flushed/replaced coolant & thermostat and all is good . I had trouble accessing the radiator petcock because my wraparound hard rock bumper and a winch were in the way. So, this wingnut deep socket from Amazon allowed me to get to it from the front easily with an extension. Adjustments.jpg


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^ good suggestion! I could have used something like that.
 

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Had 128 code, flushed/replaced coolant & thermostat and all is good . I had trouble accessing the radiator petcock because my wraparound hard rock bumper and a winch were in the way. So, this wingnut deep socket from Amazon allowed me to get to it from the front easily with an extension. View attachment 4195691


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picking one up with (can't remember the name) along with a ratcheting device to slot the tool into
 

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Had my system flushed by my local trusted independent mechanic (not the dealership). He does a full flush, unlike several other quicky places that just do a fluid exchange.
He flushes each component individually, heater core, engine, radiator. I also had him replace the radiator hoses as well as the thermostat and housing. I supplied all the parts/ fluids including the distilled water.
Coolant Flush
Upper Radiator HoseMopar 55111394AC
Lower Radiator HoseMopar 55111395AE
Thermostat + HousingMopar 5184651AH
CoolantMopar 68163848AB- 2 gal
Radiator CapMopar 52028974AA

Heat is like night and day. I never knew what I was missing. It's like it was 5 years ago when new!!
 
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