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Thread: DIY: Heater core replacement

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    Administrator Daox's Avatar
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    DIY: Heater core replacement

    So, your heat blows cool / cold out of the passenger side and you want to get nice even heat? Here is how to do it.

    Be warned, this is a pretty time intensive job. I did it over the course of a few days. It can be done in a day for sure though. I also did this two months ago, and I'm sure I don't remember every detail. Basically, you just have to keep pulling stuff apart until you can get to the heater matrix. I highly recommend taking pictures as you go because there is a lot to disconnect and reconnect.

    Lets get started!

    First, disconnect your battery. I highly recommend keeping your battery disconnected for the entirety of the repair. If you power your car up with your airbags disconnected, you'll have to have the code reset at a dealer (or possibly with ETACs decoder). Its much easier to just keep the battery disconnected until you're done.

    Now, lets remove the center console. Remove the push pins towards the front of the center console. To remove them, use a screw driver or something somewhat pointy and push the center in. With the center pushed in you can pull them out. There is one on each side.





    Use your flat bladed screw driver to pop open the little cover on the back of the center console. You will see a 10mm bolt there to remove.





    Pull up on the panel under the parking brake lever to expose another 10mm bolt to remove. The panel should pop out with relative ease. If you have plastic interior tools, I would recommend trying to pull it open from the front or sides as it'll be slightly less stressful on the rear clips.





    Unscrew the shift knob to remove it.





    You can now remove the center console. You will need to have the parking brake lever pulled up so you have enough clearance to remove it.





    Next up is to remove your glove box. To do this, open it and press the two outer edges of the glove box together and it will flip down farther. After it flips down, you can pull it off.

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    Now, we are going to remove the radio and heater controls. Start with the top section. Using plastic trim tools is a nice way to get these out without marring up surfaces.

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    Remove the screws holding the stereo in place. Then, pull the whole lower section out. You'll have a bunch of stuff to disconnect so be careful not to just yank it out.

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    Now, lets move on to the gauge cluster. The trim piece just pulls straight off. This exposes a philips head screw. Remove this and the gauge cluster can come out. I will have an electrical connector on the back to be disconnected.

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    Next up is the paneling below the steering wheel. I forget if there are bolts or screws to remove. But there is a left and right side that come off.

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    Remove the A pillar trim panels. These just pop off. You can leave them dangle unless they really get in the way.

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    Now, look in the area that your glove box used to be in. There are two bolts holding in your passenger airbag. Remove these two bolts and push up on the airbag to remove it from the dash. Be careful removing this piece as it does have sharp metal that can easily scratch up your dash.

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    On the back side of the airbag are the electrical connectors. You'll need a small flat blade screwdriver to pop up the center section on them to remove the connectors from the airbag.

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    Now, move back to the driver's side and remove the bolts around the driver's side knee airbag panel. There will be another airbag connector to remove on this airbag. Also, there are odd plastic clips holding the panel to the dash. I forget exactly how they come out, but they can be a pain to figure out. You have to pinch the clip the right way. I think one you have to pinch vertically and the other is horizontal.

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    Alright, time to remove the big dash piece! You'll have to go around and find the bolts that are holding it to the car. There really aren't that many though. There is one on each side by the A pillars, and also down below it. There are probably a couple around the center stack as well.

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    Okay, now lets drop the steering column down. Remove the four or 5 bolts that hold it up to the big metal support pipe. It will drop down. You'll probably want to unplug some of the electrical connectors going to the steering column as there isn't enough slack to let it down otherwise.

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    Now, we need to get that big metal bar out of the way. I never fully remove it from the car though since is a bit of work. You'll have to remove a bunch of wire harness connections from it. You'll have to remove the center support shown below. And you'll have to remove the bolts that hold it to the sides of the car.

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    We're getting closer now! At this point, you can pop the hood, and disconnect the hoses going to the heater core. This will require removing the airbox to get access.

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    Now, there are a few nuts holding the heater matrix to the firewall. These will need to be removed so we can pull it away from the firewall to pull the heater core out. I believe there are 3 on the top and one or two on the bottom.

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    Take a look at the left side of the heater matrix. You will see the heater core's two aluminum tubes coming out of it. Remove the electrical connectors that are in the way going to the actuators. You'll also have to remove the lower actuator from the matrix to get the heater core out.

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    Remove the two philips head screws holding the heater cores tubes.

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    Now, you can pull the heater matrix away from the firewall enough to pull the heater core tubes through. Once the tubes have released from the gasket, you can pull the heater core out of the heater matrix. The tubes on the heater core do swivel. So, take it in steps and remove it. I also suggest putting a towel down to collect any dripping coolant. You don't want your cabin to smell like coolant.

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    WOOHOO, you are finally half done!!!



    Reassembly is really just putting everything back together. Follow the steps in reverse to do it all. Phew, it was enough work just writing all this. I highly recommend if you can get your dealer to do this, DO IT!


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    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


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    this is awesome ! thanks
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    Awesome write up Doax!

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    Senior Member Cobrajet's Avatar
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    Great write-up. I will probably give this a go over the summer. Glad to see the heater case does not need to be split to get the core out.

    Did you use an OE heater core or an aftermarket replacement?

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    Moderator Eggman's Avatar
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    I'm pretty sure Daox used an aftermarket heater core - I think from Rock Auto.

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        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 49.6 mpg (US) ... 21.1 km/L ... 4.7 L/100 km ... 59.5 mpg (Imp)


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    Great writeup, Daox! Thanks.


    Looking at the in and outlet tubes of your original heat exchanger, you can see they are completely green inside. This is consistant with the gel that formed and clogged it up.


    I followed the advice of BASF/Glysantin and changed the coolant to the recommended product (Glysantin G64) months ago. Their advice in email form is in post 302 of thread " HVAC heat blows warm/hot on drivers side, cool/cold passenger side [warranty issue] "

    After recently disconnecting the hoses from the heater core of my car, there was nill deposit inside the heater core tubes, they were 100% clean as new.
    I think it makes sense to put proper coolant into the car, rather than keeping the OEM stuff and waiting for problems such as the heater core failing. I know you have'nt had the car very long.

    Another thought: Would it make sense to connect a garden hose to the core, and turn it on full blast to flush the gunk out?
    Last edited by foama; 12-04-2018 at 12:05 PM.

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    Administrator Daox's Avatar
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    Quote Originally Posted by Cobrajet View Post
    Great write-up. I will probably give this a go over the summer. Glad to see the heater case does not need to be split to get the core out.

    Did you use an OE heater core or an aftermarket replacement?
    Eggman is correct. It is an aftermarket heater core from RockAuto. It cost about $70 shipped if I recall correctly. It has been working great.



    Quote Originally Posted by foama View Post
    Great writeup, Daox! Thanks.


    Looking at the in and outlet tubes of your original heat exchanger, you can see they are completely green inside. This is consistent with the gel that formed and clogged it up.


    I followed the advice of BASF/Glysantin and changed the coolant to the recommended product (Glysantin G64) months ago. Their advice in email form is in post 302 of thread " HVAC heat blows warm/hot on drivers side, cool/cold passenger side [warranty issue] "

    After recently disconnecting the hoses from the heater core of my car, there was nill deposit inside the heater core tubes, they were 100% clean as new.
    I think it makes sense to put proper coolant into the car, rather than keeping the OEM stuff and waiting for problems such as the heater core failing. I know you have'nt had the car very long.

    Another thought: Would it make sense to connect a garden hose to the core, and turn it on full blast to flush the gunk out?
    I did attempt to flush the heater core last winter. I used a garden hose as well as letting some CLR sit in it overnight. It did seem to help a little bit, but not enough to make a huge difference.

    I would still like to test some 'flushing fluids' on the heater core. I have not yet got around to it. However, if one could flush the gunk out, it would be SO much easier than replacing the heater core.
    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


  11. #8
    I've used this https://www.amresupply.com/part/CH11...N-OPENER-909ML stuff in copper heater cores. It worked great! I'm not sure how it'd do in aluminum. I'd give it a try before replacing the core though. It had quite the reaction and the hoses got pretty hot while it was sitting. It's basically sulfuric acid.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


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    Prestone specially developed an aggressive radiator cleaner for GM (Part Number 12346500 - Heavy Duty Cooling System Cleaner) back when DexCool was causing issues. It came in a POWDER form and contained 2 materials:

    • 9 dry oz of Oxalic Acid (acid/cleaner)
    • 2 dry oz of Sodium Carbonate (neutralizer)

    It has since been discontinued. But supposedly the following 2 materials can be used to duplicate Prestone's product:

    Acid/cleaner: Wood bleach (Oxalic Acid)
    Neutralizer: Arm & Hammer Super Washing Soda

    You clean the radiator with the acid...then follow it up with the soda to neutralize it.



    I wish there were an easy way to flush it out successfully. I really don't want my dash disassembled...but I also don't want to risk the blockage getting worse over time. I'm at 57,000 miles right now so I will need to make the decision to take it in pretty soon.

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage ES 1.2 manual: 52.2 mpg (US) ... 22.2 km/L ... 4.5 L/100 km ... 62.6 mpg (Imp)


  13. #10
    I saw a video of a guy changing his heater core in a toyota I think. It was in a similar location as the Mirage but the guy uncrimped the tubes to get his old one out. Then he seemed suprissed when he found out the new one wouldn't fit in place with the tubes still attached. He eventually uncrimped the new heater core tubes, installed the core and re crimped the tubes back on with pliers. I'm not sure I'd go that route, with my luck an oring would be get torn, get pinched or I'd kink or crack something.


        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage SE wussie cvt edition. 1.2 automatic: 37.7 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.3 mpg (Imp)


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