On my 09 it was the heater core that caused the temp difference. Once I finished the CLR flush, the heater would run you out of the Jeep for most of the winter season. Somewhere on this forum, someone described using CLR in the heater core only to get some of the crud out. That would work short term for me. Yes, I tried flushing the block and changing the radiator. Seems like I could never get it 100% clean. The dealer has a notification about this and they can install a simple inline filter to help. My local dealer knew nothing about it until I made them look it up. Was going to try the filter, but traded it for my current JKU.

 

Keep us posted on what you find. Good luck!

 

Hello gang, I bought my jeep new in 12, about year later I noticed cold air driver side warm air passenger side, where as before it would blow scorching hot, I saw a thread somewhere about this sludge in the rad, Mexican casting sand, not cleaning it out after the casting process, lots of stuff out there,
at the time I worked at a lab that does all sorts of funky testing on who know what, don't ask either, any ways they did an analysis on the sludge in my overflow resivoir, go look at yours right now, bet you will find a creamy silt about an inch and a half to two inches in the bottom of it right now, turns out it is silicon dioxide and aluminum silicate primarily, a bunch of other stuff but in very low numbers comparatively, in short it is the antifreeze and aluminum from your heads, the silicate is abrasive and is either precipitating out of your antifreeze or a contaminate due to the casting process, you decide. Bottom line is it is there, it plugs up the furthest run first on you heater core ,( driver side) I wonder what the insides of our blocks look like?
ment to become a member and post it a long time ago, just never did.
Hope this helps clear it up a bit, pardon the pun

 

I had the same problem. disconnected both lines going to the heater core, in the engine compartment. used a hose to flush and backflush the heater core. (be careful with to much pressure, I wouldn't even know how to start to get to a leaky heater core)
I used about 2 gallons of water, flushing back and forth. took about 20 minutes, and has lasted a year. I think I read that the lowest part of the heater core gets clogged.
hope this helps.

 

After further exploration on my daughters sure enough the sludge is there see pic. This is truly dissappointing that this issue is up to the owner to fix and not FCA when it is directly due to there processes and/or materials used. Being this isn't an inexpensive fix in the long run I am very surprised and class action hasn't been filed yet.

 

The way I fixed it was taking the glove box out, two screws bellow it and one screw behind the goofy little hook on the centre of the dash, cutting the tubes and a portion of the dash bracket for just enough clearance to remove the core, then flushing it with a hose in the tub, a few soaks with clr and a bunch more back flushes, it comes out pretty easy, a couple pieces of 5/8" heater hose and some clamps and she is piping hot again

 

Genius solution! How did you cut the bracket? Pretty small area in there.

 

I'm fairly certain I saw either a write up that you did, or one where someone did a similar approach. Do you have a write up, or some pictures? I would love to attempt this sometime before winter gets here again next year.

Happy Jeeping!

 

My Buddy is experiencing the same issue with his 2012. The heater core is partially plugged with casting sand.

 

The 3.6L block is die cast, no sand involved. How would sand be getting in there?
Has anyone had the sludge analyzed to verify what it is?