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TJ Heater Core Replacement
for 2001 TJ 2.5L engine

by Jason Fjeld

Note from Stu:   A big thank you goes out to Jason.  Since Jason couldn't find a write-up on the site (I've been fortunate not to have any heater core issues on my TJ), he offered to share a write-up that he did after completing the heater core replacement in his '01 TJ SE.  The write-up should be close enough for other TJs such that you will certainly have a good idea as to what is required if you decide to undertake the project.  Thanks again, Jason, for helping all of us! 

And now Jason's write-up.....


So I just bought a used Jeep Wrangler with a 30-day warranty from a small local dealer. Almost immediately after the 30 days, I began to smell antifreeze, had trouble defrosting, and was noticing tiny droplets of an oily substance on my passenger floor. The obvious diagnosis was a leaking heater core. Calls to local mechanics, dealers, and small repair businesses revealed estimates of $550 to $850 dollars. The part itself was about $75 but the job was extremely labor-intensive. The entire dash had to be removed, along with the entire heater / a/c housing assembly.

To save myself several hundred dollars, I decided to do the job myself. I went on the Internet and noted a few forums where people discussed heater core replacement, but I couldn't find any detailed instructions. Wanting to share what I learned, I prepared this document. I did consult a manual by a well-known corporation (who shall remain nameless) but it was more-or-less a broad topic overview.

I hope you find this useful. Note that I am not a mechanic. I'm a desk jockey who can turn a wrench and is stubborn enough to figure stuff out. If I could do this job, chances are you can too.

Tools Needed/Recommended:
- Metric & Standard Socket Set with various extensions and socket depths.
- Metric & Standard wrenches
- Assorted nut drivers
- Torx-head Wrenches
- Channel-locks
- Phillips and Flat-Blade Screwdrivers
- Flashlight and/or Trouble Light
- Plastic Baggies
- Permanent Marker

- I removed my upper and lower doors (I have half-doors) prior to beginning the job. I wanted to be able to get under the dash with the least amount of effort and contortion.
- I found it useful whenever I was removing bolts/nuts to put those parts in a baggie and label the baggie with the particular step I was on. That way I didn't have to look at a huge pile of hardware and try to remember what went where.
- If you have a/c, it gets a little hairy since the refrigerant needs to be purged and the refrigerant lines need to be disconnected. If you are uncomfortable performing these steps and don't have the necessary equipment to keep the EPA happy, you should leave this phase to the professionals.
- Plan on a full day for the entire procedure. Or if this isn't your daily driver, do the job in phases over several days (steering column assembly, dash assembly, HVAC assembly)

The Job:

1. Disconnect and remove the battery. The negative cable needs to be disconnected to disable the air bags, anyway. It makes it a lot easier to get to the heater core hoses and housing-to-chassis nuts.

2. Drain the antifreeze from your radiator. Or, if you plan to have a professional radiator flush, you can skip this step.

3. Remove the entire steering wheel assembly, by performing the following:
- Remove the two (2) Phillips-head screws from the knee blocker and set the part aside.
- Remove the upper and lower trim pieces from around the steering column. This, too, is held by two (2) Phillips-head screws.
- Unplug all electrical connectors. Be sure to view the connector locks so as not to break any. Note that there are connectors at the top, bottom, and both sides.
- Remove the shift interlock cable (if so equipped) by turning the key to the "On" position and pressing the yellow tab. It will then slide out. Be sure to turn the key off and remove it so it doesn't get broken.
- Remove the switch bundle where it is tethered to the top of the column and allow it to hang to the bottom right.
- Remove the pinch bolt (1) securing the upper and lower steering shafts using a 13mm socket. This is located close to where the shaft enters the interior compartment.
- Remove the two (2) nuts securing the steering column to the cross-member of the firewall using a 13mm socket.
- Remove the two (2) nuts securing the steering column to the top of the firewall using a 13mm socket.
- Holding the wheel, allow it to drop down and then pull the entire assembly toward you, being careful to guide the cross member so it does not bind with the studs from the firewall.  Do NOT allow the steering wheel to spin within the column assembly as it will damage the clock spring which will then need to be replaced!  If the clock spring is damaged, you see issues with your horn, air bag light and possibly the instrument cluster when you reassemble your dash.
- Once the wheel has been removed, your Jeep should resemble this:



Figure # 1


4. Disconnect the wiring harness connectors from the 100-way wiring harness unit on the left side of the inner panel. You can access it through the hole where your steering wheel was, or from underneath the dash. I had the following connectors, viewed from top to bottom:
- Gray
- Green
- Red I
- Blue
- Yellow
- Black I
- Black II
- Red II

5. Disconnect the driver's side defrost hose at the central duct, towards the middle by twisting and gently pulling.

6. Remove the glove box by removing the tether attached to the screw behind the right upper corner of the glove box. Once that is free, let the glove box tip down until it is free of its hinges.

7. Reaching into the cavity behind the former glove box, disconnect the following:
- Two halves of the heater / a/c vacuum harness connector. This has numerous yellow and blue hoses. As you disconnect it, you'll hear the air pressure being relieved.
- Two halves of the radio antenna.
- Air bag wiring harness connector (green).
- Any other wiring harnesses you can see but I failed to mention.
- Passenger-side defrost hose at the central duct, towards the middle, by twisting and gently pulling.
- Remove the two (2) nuts from underneath the passenger's side air bag using a 15mm socket.

8. Remove the upper cover from the dash. This runs the entire length of the dash and is about 3 inches wide. Gently pry one end up and work your way to the other side. This is held on with tabs, not screws.

9. Remove the three (3) Torx-head screws from each side of the dash using a T30 Torx-head wrench, where they attach to the door pillars.

10. Remove the four (4) nuts along the window where the dash is mounted using a 10mm socket.

11. If applicable, disconnect any custom switches you may have installed to the center console.

12. Straddling the middle console, lift the dash up and out, being careful that all lines/connectors have been removed. If needed, get some assistance when removing the dash.

13. The dash, removed as an entire unit, will look like this:



Figure #2


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