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Old 10-10-2019, 12:03 PM
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Thermostat showing hot, radiator fan high, low heat in car.

Little background:
I have 2012 JK 2 door. I live in NY, so cold winter and hot summers. Last winter the interior heat stopped working. Tried a coolant flush, checked the blend door actuator, still couldn't fix it. I felt like the the coolant was getting clogged or low flow somewhere. Brought it to dealership and said it wasn't that the whole heating core need to be replaced. Didn't give a crap what I thought. Paid $2500, heating worked for the rest of winter.

Today:
For the past couple weeks of summer the thermostat is showing very warm. 3/4 of the way to Hot, instead of usual 1/2. It bounces pretty wildly between these 2 points, like a couple of seconds to go from 1/2 to 3/4. This is during normal suburban traffic. And whether at a traffic light, or driving the thermostat is still slowing bouncing all over the place. Radiator fan roars during all this. I recently went in to for a recall to the dealership and mentioned to them, they said they were only able to replicate it slightly and said it's just a little warm and not to worry...wth.
Busy with work so have just been dealing with it for a month. Now it's getting colder again outside so i turned on the interior heat. The heat does not work now. Just the same as 9 months ago.
Surely this is all related.

I feel like the the engine is getting warm but the rest of the coolant path is semi-clogged or getting poor circulation somewhere. The car is getting no heat from the heater core and when I get out of the car and move to the front while the roaring radiator fan is blowing cold air out at me and not warm in the slightest.

Any thoughts?

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Old 10-10-2019, 12:35 PM   #2
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sounds like it could be casting sand. have them fix it again then add a filter to the coolant system.

https://www.mishimoto.com/jeep-wrang...ilter-kit.html

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Old 10-10-2019, 12:51 PM   #3
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I had the exact same problem. I replaced the heater core and it still is getting sand in it, it's the low point in the system.

Temp jumping around sounds like there is air trapped.

As Ssinga said, your heater core is probably got more sand in it. I have had mine flushed twice in the last 2 months (5 times this year since Feb.). The first time no heat , drove it for a month flushed again & now I have about 120°F @ the vents. Still not as hot as it should be.

Skip the dealer and go to a reputable radiator shop to have it flushed if your not doing it yourself. Try to find one that has the machine that puts a vacuum on the system to get as much air out as possible.
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Old 10-10-2019, 01:22 PM   #4
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I would suspect air in the system and work on that idea before jumping to more serious conclusions. Indeed temp jumping around and cooler air from the rad is an indication of air.


Was your overflow tank empty for any period of time? If left empty for a good period of time you will will start sucking air onto the system. The overflow must stay between the min/max marks at all times. A lot of people don't really understand this and they let the tank go dry.


It should be noted that a leak in the system will also suck air
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heater core , hot engine , radiator fan , thermostat

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