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  1. #1
    Brian 328is
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    How to replace heater core

    I know there's several existing write ups on this in the archives. Here's my take on it.

    -------------------------------------------

    Replaced 3/6/2010
    Replaced heater core, heater core o-rings, and temperature sensors for HVAC system.
    12 hours total, including an assistant for 9 of those hours.

    -------------------------------------------

    See page 640-6 in Bentley manual

    Disconnect negative battery cable.

    Drain radiator. Drain remaining coolant in engine block by removing bolt on side of transmission next to O2 sensor. Cover O2 sensor with aluminum foil.

    Remove rear center console first. Remove two screws in back seat ashtray, then remove two screws under ashtray. Center cup holder is held in place by Velcro – no screws. Remove boot for emergency brake. I was not able to remove the rear console entirely…just enough to get at the front console.

    Remove OBC & A/C control unit.

    Loosen front console. The center front console (by the shift lever) is held in place by 8 screws – two in the rear, two on each side, and two facing up by the A/C control unit opening. One set of screws on the side, near the A/C control opening, is obstructed, and can not be removed. The shift lever boot has clips in the sides, not “front & rear” like the Bentley manual says. No need to remove the shift lever.

    Remove glove box. Remove both layers of driver’s side under dash panels.

    Remove outer front console trim. There’s a plastic nut by the rear center console for the outer trim.

    You don't have to remove the upper dash.

    Remove temperature sensors from front of heater box by pulling straight out.

    Move all wire harnesses well out of the way, towards the driver’s foot well.

    Remove the half of the heater box that's now facing the interior. I had to drill a hole in the passenger side sheet metal to access one of the screws. A long T-handle Torx wrench is a big help here. After mounting screws are removed, this piece is very difficult to get out. There are flaps for the heating & air conditioning behind this piece. You can not see the flaps with the front of the heater box installed, but these flaps will hinder its removal. A suggestion is to temporarily reconnect the A/C control unit, and try to close the flaps. If they are not closed, there’s a good chance you’ll break them (I got lucky, and didn’t break them). There’s a large black rubber grommet at the bottom of the heater box that can not be removed that makes your life very difficult here. Remove the front of the heater box thru the driver’s side, paying attention not to slice any wires.

    Remove rod & flaps from in front of heater core by removing the lever of the flaps from the right side.

    From under the driver’s dash, remove three screws from the mounting plate where the three metal pipes go into the heater core. A 1/4” pivoting U-joint adaptor for your socket is another big help here. A very small amount of coolant came out. Have some rags ready.

    Remove heater core. You will not be able to remove the heater core until you remove the three metal pipes that stick inside the core. Remove core by pivoting forward from the top, lifting up, and sliding out the driver’s side.

    Remove the old o-rings from the three metal pipes. Replace with new o-rings. Note the one of the pipes is larger than the other two.

    Install new core, placing new foam around the new core in the same places as the old one, to insure good heater operation.

    Reinstall three pipes into core. You will not be able to thread the three screws until the three pipes are fully seated into the new core.

    The rest is “reverse of removal”.



  2. #2
    robertplattbell
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    Thanks!

    I did this on my old 2002 and it was a PITA.

    I hope I never have to do this job.... ever!

  3. #3
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    Z4 heater core replacement

    Quote Originally Posted by Brian 328is View Post
    I know there's several existing write ups on this in the archives. Here's my take on it.

    -------------------------------------------

    Replaced 3/6/2010
    Replaced heater core, heater core o-rings, and temperature sensors for HVAC system.
    12 hours total, including an assistant for 9 of those hours.

    -------------------------------------------

    See page 640-6 in Bentley manual

    Disconnect negative battery cable.

    Drain radiator. Drain remaining coolant in engine block by removing bolt on side of transmission next to O2 sensor. Cover O2 sensor with aluminum foil.

    Remove rear center console first. Remove two screws in back seat ashtray, then remove two screws under ashtray. Center cup holder is held in place by Velcro – no screws. Remove boot for emergency brake. I was not able to remove the rear console entirely…just enough to get at the front console.

    Remove OBC & A/C control unit.

    Loosen front console. The center front console (by the shift lever) is held in place by 8 screws – two in the rear, two on each side, and two facing up by the A/C control unit opening. One set of screws on the side, near the A/C control opening, is obstructed, and can not be removed. The shift lever boot has clips in the sides, not “front & rear” like the Bentley manual says. No need to remove the shift lever.

    Remove glove box. Remove both layers of driver’s side under dash panels.

    Remove outer front console trim. There’s a plastic nut by the rear center console for the outer trim.

    You don't have to remove the upper dash.

    Remove temperature sensors from front of heater box by pulling straight out.

    Move all wire harnesses well out of the way, towards the driver’s foot well.

    Remove the half of the heater box that's now facing the interior. I had to drill a hole in the passenger side sheet metal to access one of the screws. A long T-handle Torx wrench is a big help here. After mounting screws are removed, this piece is very difficult to get out. There are flaps for the heating & air conditioning behind this piece. You can not see the flaps with the front of the heater box installed, but these flaps will hinder its removal. A suggestion is to temporarily reconnect the A/C control unit, and try to close the flaps. If they are not closed, there’s a good chance you’ll break them (I got lucky, and didn’t break them). There’s a large black rubber grommet at the bottom of the heater box that can not be removed that makes your life very difficult here. Remove the front of the heater box thru the driver’s side, paying attention not to slice any wires.

    Remove rod & flaps from in front of heater core by removing the lever of the flaps from the right side.

    From under the driver’s dash, remove three screws from the mounting plate where the three metal pipes go into the heater core. A 1/4” pivoting U-joint adaptor for your socket is another big help here. A very small amount of coolant came out. Have some rags ready.

    Remove heater core. You will not be able to remove the heater core until you remove the three metal pipes that stick inside the core. Remove core by pivoting forward from the top, lifting up, and sliding out the driver’s side.

    Remove the old o-rings from the three metal pipes. Replace with new o-rings. Note the one of the pipes is larger than the other two.

    Install new core, placing new foam around the new core in the same places as the old one, to insure good heater operation.

    Reinstall three pipes into core. You will not be able to thread the three screws until the three pipes are fully seated into the new core.

    The rest is “reverse of removal”.


    Thanks for the post, it's great help! just one follow up question: did you depressurized the A/C lines before removal of the heater core unit? Thanks,
    Reply With Quote Reply With Quote 75.167.189.157

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