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Thread: how to seal up new floor plugs?

  1. #1
    Join Date
    Jun 2016
    Location
    Austin, TX
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    1,161
    My Cars
    1978 323i

    how to seal up new floor plugs?

    I've bought new "cover lids" for the large holes in the floor and trunk of my car (part # 41128200462) as well as the smaller plastic ones and I'm wondering, what's the best way to seal these to the car?

    The smaller plastic ones have a white ring around them that I'm thinking might be heat-glue. Would I heat them up with a hairdryer after installing to seal?

    The larger metal ones had a bunch of seam sealer slathered over them, but it looks like it was done after installation, which didn't keep water from getting in the cracks from below.

    Can anyone confirm the "right" way to do these? Would it be smearing seam sealer around the lip before and after installation, then painting over after its dried?

    plug.jpg

  2. #2
    Join Date
    Jun 2005
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    Chicago
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    My Cars
    BMW 320i ('83), BMW 318ti ('98), BMW 3.0 CSi ('72)
    I replaced the large metal plugs when I did the rebuild on my S52 swapped E21. I don't know what the "correct" way to do this is, but I sanded to metal the area around the large plugs and then coated the area with a rust protection application I had purchased from Eastwood. Thereafter, I used a seam sealer I had purchased from Eastwood as well and then applied before placing the plugs and after to ensure there were no gaps or openings. Only time will tell if this would hold up.

  3. #3
    Join Date
    Jun 2016
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    Sounds good, thanks!

  4. #4
    Join Date
    Oct 2004
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    Ohio
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    6,754
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    E21 320i, e39 540i/6
    Clean all old rust, undercoating, and seam sealer from the floor pan holes. I use a twisted wire wheel on an angle grinder for this type of work. If there's any pitting or rust left over I recommend treating it with something like naval jelly or evapo-rust before final cleaning and priming. If there is any remaining rust, I've used a rust converter followed by a zinc rich etching primer.

    Degrease the new plugs (if they're oiled) and prime using a zinc rich etching primer. Let everything cure before installation in to the floor.

    Final step is a brush-on seam sealer top and bottom to seal up the joint, followed by rubberized paintable undercoating on the floor, followed by a top coat of paint.

    '81 320i turbo | t25, 931 CIS, 240hp, 13.92@100mph | 2.2L m10 Turbo Build | My E21 Videos |

  5. #5
    Join Date
    May 2005
    Location
    Red White and Blue
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    450
    My Cars
    82 E21
    Great advice from all previous posters.

    FYI - Dynatron 550 seam sealer has been my go-to for this type of work. It is fairly inexpensive, readily available at most auto parts stores and stays flexible when dry. It also takes paint well.

    It comes in a tube that will fit a standard caulk gun and you can use a cheap paint brush to give it that factory look/push it into the gaps.



    MJ

  6. #6
    Join Date
    Mar 2020
    Location
    Chicago
    Posts
    4
    My Cars
    BMW X6
    For smaller plasitc ones you can use Bob Smith Industries Maxi-Cure. It has a very thick glue formula and sets almost instantly. there will be no need to heat tehm up. For bigger parts you an tale a look at prodducts of 3M. Their glues are iften used in cars.

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