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The heat doesn't work properly (and it overheats which is another issue.) in the truck so we figured that there's air in the cooling system. But we had trouble finding where they are. Can anyone show a diagram or description of where it is located?
 

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07Lifted,4X4,6sp-man,3.7L
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Welcome to the forum @L S. When you have a chance, head over to the Newbie Section and say "Hi".
Tell us a little about yourself and your ride.
That way we can welcome you all proper like.


I am not aware of a bleeder valve on the 4.0 like the 3.7 has.

This is the procedure you need to follow.
To properly de-aerate the system after any engine cooling system maintenance, you should fill the fluid in the reservoir to the full mark and put the cap back on. Start the rig and turn the heater on "High" heat (the heater fan has to be on, but at what level does not matter).

De-aeration does not occur at engine idle, higher engine speeds are required. Normal driving will de-aerate the cooling system.
After the rig reaches operating temp, shut it off and let stand till completely cold.(Leave the fluid cap on during cool-down!) Refill the reservoir again and repeat 3 more times.

Some here with the 4.0 have had more success removing the air with the rig raised on the side with the radiator cap(ie a ramp on only that side). Cap off, start rig, watch coolant level inside radiator, and fill as air burps out.
Don't over fill or coolant will spill out, It WILL be HOT, and you don't want any in your eyes or mouth!!!

Only use HOAT coolant in the Nitro!
Zerex G-05 is what I use. It meets Mopar HOAT standards (MS-9769).
 
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07Lifted,4X4,6sp-man,3.7L
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Digging way back in the forum threads I did find one post about a 4.0 bleeder.
I have a 3.7 so I can not visually look at mine to verify if this is true, or if it will get the air out because the location is physically lower then heater hose level.
Found the coolant bleeder. On a 4.0 it is accessible from the passenger side at the rear of the engine on the thermostat housing. It is under the air plenum and you need a 10 mm socket and wobble to open it. I missed it on the engine I pulled because a tag hanging on the fuel rail had it covered.Very useful if you have any cooling system trouble and need to refill or want to do a flush and refill when the coolant reaches the end of its lifespan. With the engine cold just crack it open and slowly inventory the radiator until you get flow from the bleeder and close it.
What I posted in post 2 is the SM recommendation if you do not have a vacuum filler.
 
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