btadlock

2009 JKU, and as it has been wicked cold here, I have noticed an issue with my heat.

The two vents on the dr side, (out by the door and the left one in the middle of the dash as well as the left side of the defroster), Temp up all the way on the dial, the dr side is considerably colder than the passenger side, almost straight up cold air, while the vents to the passenger side seem to be much warmer, but perhaps not as warm as they have been in the past.

The heat at times in the past could be too much, but no longer.
Ideas?
Thanks

JKZinger

You have casting sand in the heater core. Had mine replaced and I have hot air in all vents again. Not a cheap fix though. It has been an ongoing problem since the JK came out. Mine is a 2010

Vintage

Sounds like the HOAT vs OAT symptom.

Suspected Heater Core Issues, and An Interesting Situation... - JKowners.com : Jeep Wrangler JK Forum

Vintage

Here's a nice thread from this forum

https://www.jk-forum.com/forums/stoc...oolant-339094/

btadlock

is replacement the only solution? will flushing provide any improvement?
Thanks.

mglad1

I saw video on YouTube that a guy was able to flush his clear. But some say it can't be done. The dealer replaced mine under warranty luckily. I think a flush is worth a try.

btadlock

I have searched YouTube and found many heater core flush videos, helpful to understand the concept, but did not find one specific to the JK.

I looking at the JK and then the TJ, the TJ looks simple, like most of the videos, two hoses into the firewall for the heater core, but the JK does not look as clean. I guess that would need to disconnect the hoses at the engine end to flush.

to enable a reverse flow flush, which hose is the heater core supply side, the upper or lower hose? and by upper and lower, I mean the connection points on the engine, one connects higher on the engine than the other.
Thanks.

mglad1

btadlock,
The video I was able to watch, the guy flushed both ways. So will it matter when it comes to flushing which one you start with? If I remember correctly some air pressure was introduced to help eliminate excess water when he was completed. Just remember which line came off which connection.

btadlock

Well, that certainly takes the guesswork out of it, the simple, obvious solution escaped me.

Thanks

zzodo

I had an 09 with the same issue. Just like what everyone said above, heater core. Somewhere on the forum, someone talked about using CLR in the heater core ONLY! Not in the whole system. I did that a couple of times, then would flush with distilled water, then use an air line to blow everything out and finally put the system back together and use the correct coolant. While I had the heater core soaking in CLR, believe I'd do that for 30 minutes, I'd flush the engine, radiator and overflow tank. This would work most of the winter season. I would do this every November. I would have had the heater core changed, but I was out of warranty and couldn't be without the Jeep as long as they needed it.