Very little heat from new heater core

-T.

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Feb 24, 2017
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Mount Prospect IL, United States
Another update: I was wrong. Outside temperature was down this morning and heat in the Jeep was pretty weak. I have a new project for the cooling system, so I'll be messing with it more in the next day or so. So more burping will be done. I will have the heater hoses off again, so I'll be starting fresh anyway. I'll put the Jeep on ramps this time.
 

-T.

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Feb 24, 2017
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Mount Prospect IL, United States
Another update: Had the Jeep running for an hour or more, nose in the air shaking and squeezing hoses like a mad man, but no love. Everything was good and hot and recirculating. I found my thermometer and could get about 100 degrees from the vents if I ran the blower on low. If I cranked it up, the temp would drop to about 90. Digging around here, I found references to temps at the vents being 135-145. I am going to try another core. Yay.
 

-T.

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Feb 24, 2017
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Mount Prospect IL, United States
Thermostat is 2 years old, and the Jeep is running fine. We just did 2500 mile trip last fall without issue. The heater core, which has be showing signs of leaking for quite some time, just got bad enough for me to decide that it was time to replace. Before the heater core change, I had good (great) heat and no other cooling problems. After the heater core, I have weak heat and no other cooling problems.
 
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Reactions: VallenMaes

-T.

TJ Enthusiast
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Feb 24, 2017
Messages
268
Location
Mount Prospect IL, United States
Final (hopefully) update: So I got another heater core from Rock Auto. I tried a couple small experiments to try to see if there was any significant difference between new heater core #1 and new heater core #2, but I didn't see anything that made me sure that new core #1 was defective. I decided to just dive back in and swap it. Getting the dash off and HVAC unit out is much quicker the 2nd time! With the new heater core in, and the HVAC unit back in the Jeep, but not even fully bolted in, and the dash just moved close enough to make all the connections to run the heat, I started the Jeep and bled the cooling system again. And the heat immediately went right to 160 degrees (my thermometer was closer to the heater core at that point) So, I reassembled everything and ran the Jeep again and I have 140 degrees at the vents. So, it was new core #1 all along. I don't know whether I want to return it to get my 36 bucks back, or disassemble it to find out what is wrong with it.
 

RMETeeJay

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South Platte Valley
Do it for science! If for nothing else so they won’t sell it to someone else.

There are plastic corkscrews inside the passages. Maybe one of them is wonky?