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Old 10-31-2019, 12:15 PM
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Tell me it's not the heater core, please...

04 TJ, 4.0, 157K

It's cold here in Texas, so now I'm faced with the sick/sweet smell of antifreeze when I turn the temp knob from blue to red. I replaced the thermostat this week and was hoping I was just smelling the external leak.

From what I've read here, I'm having some but not all of the bad heater core symptoms:

-Smell is only for less than a minute when either the Jeep is started with the heat on or I switch the heat on. It's not a constant smell.

-The windows don't fog up, defrost works fine

-There's no leak onto either floor board, I looked under the carpets

Could it be anything else? I've watched the videos on HC replacement and I really don't want to tackle that big of a job. Thx

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Old 10-31-2019, 12:26 PM   #2
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You could try leak detector dye or wait until it starts leaking on the floor to be sure it's the heater core but in my experience that's most likely going to be the heater core.
https://www.amazon.com/FJC-4926-Univ...s%2C244&sr=8-7

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Old 10-31-2019, 12:33 PM
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Thx, I assume I just pour into the radiator? Would a leak somewhere else in the system cause the smell in the cab when the heat comes on?
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Old 10-31-2019, 04:31 PM   #4
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The only place it comes into the cab and a/c][Heater system is from the heater core so not likely.

Yes you just pour it in and run it to operating temp for awhile (turn the heater on). If it's just starting to seep from your heater core and not hitting the floorboard yet you might not see anything though. You'll need a UV light, some yellow glasses and a darkened garage to see the dye.
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Old 10-31-2019, 06:02 PM   #5
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Just replace the heater core... ur gonna do it soon anyhow....
Ps yes it's the heater core
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Old 10-31-2019, 08:06 PM   #6
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Replacing the heater core seems daunting at first, but really its not that bad once you start. Just label everything and bag and tag all fasteners in separate bags for each step. The worst part is getting both nuts off the stud directly behind the engine. Also just a thought but if you have air conditioning it is a good time to replace the evaporator.
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Old 11-01-2019, 08:25 AM   #7
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When the core begins to fail, that is exactly what you find.

I had all those same symptoms when I took mine out for test drive before completing the sale. Seller replaced it before I took delivery.

He showed me the old one. The core weeps coolant when they start to fail. Not a lot, but enough to smell that sweetness when the heat was turned on. Then it dries up while the heat is running.

That is how they start, just before they get to the point where fluid is on the floorboards. Maybe you could get another season before having a full blow-out. Who knows? I know that when things like this happen to me... It is always when it is -20F or 102F out. The worst possible timing is guaranteed!

Why risk no heat/defrost when it really does get cold? Replace now, if you can.
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Old 11-01-2019, 11:01 AM
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Thanks everyone. Bummer since I JUST replaced AC o rings, receiver dryer, and charged the system in July. I hate the thought of renting the gauges and recharging once I jump all of the heater core hoops! That was a pain. My other issue is finding someone to evacuate the system for a reasonable price... but I guess I have no choice. Unless I want to pay $1000 to have it done. (Which I don’t )
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Old 11-01-2019, 01:12 PM   #9
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Mine was repaired before I took delivery, but my guy just replaced the heater core and left the AC alone. While it is a great idea to replace the evaporator and other aging AC components before they fail... It is not a rule that you have to.

Yes. It would suck to take the dash and all that apart a second time, should the AC fail on you later. But, if you can't afford that and "it aint broke", then leave the AC alone and just go with replacing the heater core. Worst case... You live without AC for a while, if it does crap out on you later.
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Old 11-01-2019, 09:53 PM   #10
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Go to Harbor Freight in purchase a set of gauges and vacuum pump and then you'll never have to pay someone to work on your AC again
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Old 11-03-2019, 11:54 PM   #11
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Quote:
Originally Posted by TX TJ View Post
Thanks everyone. Bummer since I JUST replaced AC o rings, receiver dryer, and charged the system in July. I hate the thought of renting the gauges and recharging once I jump all of the heater core hoops! That was a pain. My other issue is finding someone to evacuate the system for a reasonable price... but I guess I have no choice. Unless I want to pay $1000 to have it done. (Which I don’t )
I have an 06 tj 2.4. Did the heater core in a matter of hrs. Dash is so simple Ulll be good in no time
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Old 11-08-2019, 09:50 AM   #12
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5 to 6 hour job depending on skills. IMHO I would replace both the HC and evaporator core while you're in there. Just take your time and assume the job will take all day.
No special tools required except for AC stuff. Also be careful with the plastic door light plungers in the door frame at the dash panel, I broke mine and had to get new/used ones. I'd just remove them. You do not need to totally remove the dash. The standard instructions say to remove the steering column so you can remove the dash. If you just remove all dash fasteners, you can suspend it from the roll bar at an angle with string to easily get the box out. This will also prevent you from accidentally damaging the clock-spring by turning the steering wheel too far. Be careful with the white Styrofoam cushion in the box as you cannot buy another one. I had to RTV mine back together. It's required for proper airflow. Good luck!
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Old 11-11-2019, 01:09 PM
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Thanks for the tips RFH_98TJ.

OK, I think I'm gonna dive in. Any thought on which brand heater and evaporator core to buy? Omix-Ada? Car Quest? Mopar? The heater core part itself ranges from $40-$240.00 in a quick search. Pretty huge difference in price in both parts.

Anything else I need to have on hand besides freon and A/C removal tool? Thx
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Old 11-12-2019, 05:24 PM   #14
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I have no experience with those brands at all so take this for what it's worth but for a part that is that hard to replace I would go with Mopar every time.
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Old 11-12-2019, 06:07 PM   #15
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I have a YJ, so your TJ may be different enough that what I'm about to suggest doesn't totally apply.

I think you might be able to access your heater core without discharging your AC system.

As far as what part to buy, I suggest a MOPAR part.
The pics show what differences I found when I bought an aftermarket heater core for my YJ. IIRC, the core was around $69.00.
The aftermarket core was smaller and when I went to fit it to the housing, the stock screws touched the tank. It looked like a leak wanting to happen.

Faced with the dilemma of trying to fit an inferior part into me Jeep in a way that it will be a permanent fix or buying a MOPAR core (if even there was one available for a YJ) I looked for a good used one.
I ended up taking the stock heater core to a radiator shop. They charged $50.00 to boil it out, solder the leak and pressure test it. That was 3+ years ago. So far, no problems at all, and I have great heat & defrost.

I think a lot of heater cores get damaged when an owner or mechanic twists the heater hose to remove it from the heater core. This twists the neck of the tube loose from the body of the core and starts a leak.
The correct way is to slice the heater tube along the top of the heater core tube with a utility knife. Then, peel the hose off the tube without twisting.
Lube the new hose with dish soap when installing.

Let us know how it goes for you.

Good Luck, L.M.
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Old 11-12-2019, 09:19 PM
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A guy at Quadratek told me a lot of Mopar parts are actually made by Omix-Ada or Crown, etc. Anyone know about the heater and evaporator cores? Luckymac, I was going to do evaporator core since it's right there, so that's why I was planning on draining the A/C system. I may look into preparing the core as you suggested.
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Old 11-12-2019, 11:17 PM   #17
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Doesn't matter anyhow... on the tj you have you disconnect the ac as the evaporator and heater core are both inside the hvac plenum which must be removed as a unit...

Also, the mopar tj core is aluminum with plastic tanks and it is the plastic that fails... there's no rebuilding them...

I chose a murray core from O'Reilly's.... I've put that brand in many vehicles over the years and haven't had one fail yet...

Op I would suggest that you set aside 2 full days for this... you may well get it done faster but leave yourself open in case you don't.... it's a big enough hob that you don't want to take it apart twice... ALSO look at my dash speaker thread in my signature.... might be worth mounting some tweeters while ur at it....
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Old 11-13-2019, 10:21 AM   #18
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I have a Spectra brand evaporator and Advance Auto's house brand HC. It's been more than 3 years and they are working fine. Just be gentle with anything you buy. Those long tubes can be fractured loose easily and will leak. With the Advance Auto standard 20% discount they were both less than $50 each if I recall.
After you get the box back together, make sure ALL of the doors work freely or you will be removing it after you install it. The main blend door has a habit of jumping out of the indents for it. See the pic below and you can see where mine was not in the indent. I drilled a small hole and used an awl to keep it in the dimple. Be gentle with the actuating arms for the doors. Quadratec sells them if yours are damaged.
Another thing to consider is to make sure that the foam rubber block is in decent shape where it presses into the firewall. I added a little extra non-absorbing foam (mouse pad scrap) to mine so it seals good. This is a spot where rain water can get in and drip on the passenger floor.
Make sure you add the elbow back onto the drain when all done.
One more thing that hangs people up. The stud on the back side of the valve cover has 2 nuts on it. The first secures the cowl drain, the second is the one that secures the HVAC box. Many only remove the first and don't realize there is a second.
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