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13 JK Reverse Flush Heater Core

27K views 11 replies 10 participants last post by  paradocs78 
#1 ·
I have a 13 jk that I purchased used last year. I am one of the many having issues with my drivers side heat. The drivers side is blowing 20 degrees colder than the passenger side using a temp gun.
I had the coolant flushed by a local shop and the issue is still there. They used the green coolant which is supposed to be universal. Hopefully that's not an issue.
I then found the reverse flush of the heater core as a possible solution.
The question I have is does anyone have any pics of which hose is the in or the out on the 3.6. I was also wondering if people are doing it near the water pump or close to the heater core.The majority of the videos I have seen are on the 3.8.
The other issue I see people discuss is the blend door. My blend door does not click and I do hear it working if I move it from cold to hot. So I guess that means its working

I would like to try the reverse flush tomorrow so any help would be greatly appreciated.
Thanks,
Luis
 
#2 ·
A coolant flush won’t fix it. It’s either the control, blend door or another door not functioning. You can tell this by the difference in temp from side to side...a heater core makes one temp, hot! ...then the doors regulate within the vehicle.


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#3 ·
A coolant flush won’t fix it.
I disagree. This is a very common problem that's most often fixed with a properly done reverse flush of the radiator core. If all that's done is putting radiator cleaner in, that's unlikely to fix it.

Best procedure is to get engine up to temperature, then disconnect the hoses from the heater core and put radiator flush directly in the core. After it has a chance to work, connect a garden hose to the core and flush it in the reverse direction.



In the photo above, the hoses pictured below are attached to the hoses leading to the radiator core; the green hose is looped to both aluminum tubes to prevent coolant from flowing out of the radiator.

Hoses like this will do the job, they get connected to the core hoses where they're removed from the aluminum tubes.



This is the procedure a Jeep dealer mechanic recommended to me when I had the problem; he even recommended that I do it rather than me paying them to do it.

This procedure fixed the problem.
 
#8 ·
I plan to do a complete flush and I love all the info that's been shared. My question concerns what coolant to put back into the system after the flush. I know a lot of people think the debris found in the HC is a result of sand left over from the casting process. However, could it be that the coolant that Jeep is using is breaking down and creating debris as well?

I've seen some folks go back to "the green stuff" old school anti freeze. Is this something that should be done? Or should I stick with what Jeep uses from the factory?
 
#10 ·
Go back to Jeep spec for your year Jeep. It's already in the manual no to mix the coolants and not to use universal coolant either.

I just saw a 2012+ Jeep get it's engine replaced after constant overheating issues, the engine channels were crusted shut. It was a mess. I don't know if they mixed coolants or just had the dreaded "casting sand" issue, but it wasn't good.
 
#11 ·
1 - You can verify if the blend door is working correctly with a Harbor Freight inspection camera.
2 - Reverse flushing the heater core will restore heat to the driver side. I reverse flushed mine for 2 days with a small Harbor Freight pond water pump in a large bucket of radiator/heater core flush fluid.
 
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