Very little heat from new heater core

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.
 
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.
 
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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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.
 
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?
 
Just read this post and we have the same problem - no heat after replacing the leaking heater core. The new core was gotten from NAPA. We have also replaced the all cooling system hoses, water pump, radiator, thermostat and thermostat housing. The heater actuator motor is turning when you turn the control knob. We have also disconnected the heater hoses at the water pump/temp housing and tried to add coolant into heater core through the upper heater hose and coolant ran out the lower hose. So there is no air in the heater core. When the engine is up to temperature there is no heat coming out if the vents. So I guess we will be ordering a new heater core and replacing it again.
 
I know this is an old thread, but I have also just finished replacing a new Spectra heater core because of no heat. There seems to be a common thread here, so if you're getting ready to replace your heater core and don't want to do it twice....
 
As a Hail Mary, try stopping on a good sized incline, front end up high. See if this can get the heat flowing. Just remembered a Nissan I had that had a small pinhole leak in the head gasket. For some unknown reason gasses would collect in the heater core and I would loose almost all heat. If I parked nose up on a good sized berm for a minute or two with the engine running the air would burp out and I'd have heat for the next 100 miles or so.
 
Just read this post and we have the same problem - no heat after replacing the leaking heater core. The new core was gotten from NAPA. We have also replaced the all cooling system hoses, water pump, radiator, thermostat and thermostat housing. The heater actuator motor is turning when you turn the control knob. We have also disconnected the heater hoses at the water pump/temp housing and tried to add coolant into heater core through the upper heater hose and coolant ran out the lower hose. So there is no air in the heater core. When the engine is up to temperature there is no heat coming out if the vents. So I guess we will be ordering a new heater core and replacing it again.

I replaced my heater core in July of this year. The reason I did so was because I had to remove the HVAC box due to the fact that I could not get the air to come out of the vents in the dash, or the defroster. The air would only blow onto the floor.
After removing the center vent bezel, I discovered that one of the vanes in the deflector had come loose and fallen down to the bottom of the HVAC box, jamming the blend door.
The heater was working fine at the time. But....in an attempt to head off problems at the pass...I decided to put in a new heater core. That turned out to be a mistake. As luck would have it, and since it was July, I did not check to make sure the heater was working properly. At the time, I was only concerned about the A/C working, and cold air blowing out the dash vents. That much of the mission was a success .

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I don't drive the Jeep much in the winter because of the salt they spread on the roads here. Last month the wife and I decided to take a drive out to the west desert, along the old Pony Express Trail, to see if we could spot any wild horses. That's when we discovered the heater was not working. Have you ever taken your sweetheart on a road trip with the heater not working? No bueno.

I checked the for the usual problems. Air pocket? Nope. Bad thermostat? Nope. Water pump failure? Nope. When I touched them, both heater hoses were so hot that I could only hold my hand on them for about a second. I unhooked both hoses and ran water through the core, no problem there. Using an air hose, I could blow through with no problem as well. All the blend doors were working normally, the heater fan worked on all speeds and I could feel the end of the temp blend door axle and it was rotating when I turned from hot to cold and back.

Today I bit the bullet and decided to remove the new heater core. I had purchased one from Napa, it says Spectra on the sticker. I used a small flashlight to look inside it and could see something that looked like it should not be there. My curiosity made me open the thing up and here is what I found inside.

Luckily, I kept the old heater core, (the one that was working just fine). When I looked inside the old one. I can see that there are no plastic inserts in the tubes. I do not know why Spectra would put these inserts in the tubes, but it apparently affects the efficiency of the heater core. I plan on reinstalling the old heater core tomorrow.

I included a gratuitous photo of the wild horses, it was a herd of about 50.

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I don't drive the Jeep much in the winter because of the salt they spread on the roads here. Last month the wife and I decided to take a drive out to the west desert, along the old Pony Express Trail, to see if we could spot any wild horses. That's when we discovered the heater was not working. Have you ever taken your sweetheart on a road trip with the heater not working? No bueno.

I checked the for the usual problems. Air pocket? Nope. Bad thermostat? Nope. Water pump failure? Nope. When I touched them, both heater hoses were so hot that I could only hold my hand on them for about a second. I unhooked both hoses and ran water through the core, no problem there. Using an air hose, I could blow through with no problem as well. All the blend doors were working normally, the heater fan worked on all speeds and I could feel the end of the temp blend door axle and it was rotating when I turned from hot to cold and back.

Today I bit the bullet and decided to remove the new heater core. I had purchased one from Napa, it says Spectra on the sticker. I used a small flashlight to look inside it and could see something that looked like it should not be there. My curiosity made me open the thing up and here is what I found inside.

Luckily, I kept the old heater core, (the one that was working just fine). When I looked inside the old one. I can see that there are no plastic inserts in the tubes. I do not know why Spectra would put these inserts in the tubes, but it apparently affects the efficiency of the heater core. I plan on reinstalling the old heater core tomorrow.

I included a gratuitous photo of the wild horses, it was a herd of about 50.

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I seen a while back where someone pulled something similar out of their block, where the water pump attaches.
 
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I wonder if those are something from the manufacturing process that was mistakenly left in or if its supposed to serve a purpose like swirl the coolant through the tube? If the later, why?
 
This forum never ceases to amaze me. Thanks to @MountaineerTom for linking us to that thread, where we found out through @jmitchell418 and @JeepKub that those twisted pieces are turbulators. @Jeffrey Hamre even posted pictures of the new and old turbulators and mentioned the problem that the new ones caused even if he didn't quite get what turbulators actually do.

FWIW, Turbulator, when used in Italian, is turbolatore, very similar in spelling to radiatore which is pluralized to radiatori because there can never be too much pasta, so I don't think I was too far off thinking about noodles, which are a type of pasta.
 
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I am happy to report that I finished up the reassembly today. I reinstalled the old heater core that I had saved, and now the heater blows warm air just as it should. I thought about removing the noodles and putting the new core back together. The one issue that kept me from doing it, is the way the end tank is crimped to the tubes and fins. I was afraid that I might not be able to make all the crimps correctly and the dang thing would leak. It is such a pain to remove the dash and HVAC box that I decided not to take the chance.
Tomorrow I am off to my local mechanic to have the A/C recharged.
 
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I to have been battling the same problem. After reading your post I went and purchased a new heater core. I made a way to test it. I hooked a hose and a garden hose end on the new core. I hooked it to my laundry sink. Ran hot water thru it. The whole thing got hot.
so I took the older new one out of my Jeep. Tested it the same way and only about 1/3 of that core got hot.
so I installed the newer new on. I now have hot heat way before the engine even heats up all the way.
FYI both of mine had Spectre on them even though the boxes didn’t.
Spectre must make them for a lot of companies.
 
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I replaced my heater core last year and the heat has never been the same I am going to try some of these suggestions but I hope I do not have to replace the heater core again.

My situation is the heat will kinda work at 1 or 2 but anything more than that will start being cold. It also takes a long time to be warm as well. Like the engine temp is good but I need to wait like 10 mins past when it arrives at 200-210ish. Would y'all say it is the heater core is bad?