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Thread: Seeking advice on quarter panel repair (pics included)

  1. #1
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    Default Seeking advice on quarter panel repair (pics included)

    I will be replacing the rear quarter panel on a 2002 Subaru Impreza. Most of the perimeter of the panel will attach at pinch joints, so I anticipate doing typical plug welds in those locations. The two areas I am seeking advice on are where the replacement sheet metal joins the existing sheet metal at the rocker and at the upper end of the C-pillar.

    My plan is to use the backing strip method in both locations, but my two questions are:

    1) What is the best way to protect the seam on the backside in the rocker area (where I can’t get access)? The only idea I had so far was to put in a relatively large access hole adjacent to the area and plug later, but maybe there is a better approach…

    2) Should MIG plug welds be used as an alternative to spot welds in this case (i.e. car is 2002, not sure if the “modern” sheet steel presents any issues in that way).

    The first picture shows the two areas where I think I need to use the backing strip method and the second picture is the replacement sheet metal (I am using a genuine Subaru part FWIW). I have a Lincoln MIG welder and use a typical argon/CO2 mix.

    I have done some similar sheet metal welding on an older car, so I am not totally green, but definitely not an expert either.

    I really appreciate the consideration!

    repair locations.jpgq panel.jpg

  2. #2
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    The access hole is a good method but then you have unprotected area where you filled the hole. You can drill a small hole and use 3m's Cavity Wax with their wand kit, That way you only have a small hole to fill and you could do it with a rubber plug. If you use the Cavity Wax apply one coat, wait a couple hours then apply another coat, the heavier the coating the better.






  3. #3
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    Hello Len,

    Thank you very much for the reply... this is probably how I am going to go... Is the cavity wax similar to cosmoline? If so, do you think one or the other is better suited to this application?

  4. #4
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    Quote Originally Posted by 500_19B View Post
    Hello Len,

    Thank you very much for the reply... this is probably how I am going to go... Is the cavity wax similar to cosmoline? If so, do you think one or the other is better suited to this application?
    I've never used cosmoline so I have no comparison. The Cavity wax works but it takes a couple of coats.

  5. #5
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    Quote Originally Posted by 500_19B View Post
    Hello Len,

    Thank you very much for the reply... this is probably how I am going to go... Is the cavity wax similar to cosmoline? If so, do you think one or the other is better suited to this application?
    they'll both do the job, the cavity wax might be easier to apply with the wand. if you have the cosmoline already, and have a way to shoot it into the cavity it'll work. i only use cosmoline on equipment, but i don't see any reason why it wouldn't work here. i've seen 40 year old cosmoline still doing the job.
    b marler

  6. #6
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    Quote Originally Posted by 500_19B View Post
    I will be replacing the rear quarter panel on a 2002 Subaru Impreza. Most of the perimeter of the panel will attach at pinch joints, so I anticipate doing typical plug welds in those locations. The two areas I am seeking advice on are where the replacement sheet metal joins the existing sheet metal at the rocker and at the upper end of the C-pillar.

    My plan is to use the backing strip method in both locations, but my two questions are:

    1) What is the best way to protect the seam on the backside in the rocker area (where I can’t get access)? The only idea I had so far was to put in a relatively large access hole adjacent to the area and plug later, but maybe there is a better approach…

    2) Should MIG plug welds be used as an alternative to spot welds in this case (i.e. car is 2002, not sure if the “modern” sheet steel presents any issues in that way).

    The first picture shows the two areas where I think I need to use the backing strip method and the second picture is the replacement sheet metal (I am using a genuine Subaru part FWIW). I have a Lincoln MIG welder and use a typical argon/CO2 mix.

    I have done some similar sheet metal welding on an older car, so I am not totally green, but definitely not an expert either.

    I really appreciate the consideration!

    repair locations.jpgq panel.jpg
    Why replace the sail panel area ? If that were my car I would cut off sail panel section of the new panel and lap weld the new quarter at the base of the old sail panel area.

    And why not just do a lap weld in the rocker area ?

    Is this a replacement due to rust damage ? The picture is so small I can't tell if there is any collision damage or not.

  7. #7
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    Thanks everyone for the feedback!

    Phil, in response to your questions: It is collision damage. the majority of the damage is along the midline of the quarter, basically at the base of the sail panel all the way back to the leading edge of the taillight. The lower half of the sail and the connection jam are quite bent, and access to the back side of the sail is poor as there is other structural sheet metal in the way. Fortunately, all the damage is confined to the outside skin (it was a grazing along a wood barrier). The bottom of the wheel arch, forward side, is also damaged and there are a few holes for a small trim piece which will be difficult to recover due to access. However, I am thinking about what you said about the optimum cut-in locations. I am not near the car right now, but over the weekend I will try and get some pics. The pic I attached is pre-damage.

    This will be an obvious newbie question, but when you refer to lap weld, I think I understand that means to have one side of the sheet metal at the joint slip under the other side and weld along the edge of the outer piece and then finish the offset with filler? It seems clear for the sail panel area, but where would you place the lap for the rocker?

    Really appreciate the input I am receiving here!

  8. #8
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    Quote Originally Posted by 500_19B View Post
    Thanks everyone for the feedback!

    Phil, in response to your questions: It is collision damage. the majority of the damage is along the midline of the quarter, basically at the base of the sail panel all the way back to the leading edge of the taillight. The lower half of the sail and the connection jam are quite bent, and access to the back side of the sail is poor as there is other structural sheet metal in the way. Fortunately, all the damage is confined to the outside skin (it was a grazing along a wood barrier). The bottom of the wheel arch, forward side, is also damaged and there are a few holes for a small trim piece which will be difficult to recover due to access. However, I am thinking about what you said about the optimum cut-in locations. I am not near the car right now, but over the weekend I will try and get some pics. The pic I attached is pre-damage.

    This will be an obvious newbie question, but when you refer to lap weld, I think I understand that means to have one side of the sheet metal at the joint slip under the other side and weld along the edge of the outer piece and then finish the offset with filler? It seems clear for the sail panel area, but where would you place the lap for the rocker?

    Really appreciate the input I am receiving here!
    Yes (more or less) to the second paragraph.

    I would like to see a picture or two of the damaged quarter. Those kind of repairs were my favorite jobs for close to 40 years. I'm an expert painter but if someone asked me "which do you prefer, body work or painting" ? It would be body work hands down. Back in 1971 when I started bodywork/painting professsionally just about all the shops hired "combination men". Meaning they wanted body men who could also paint. In this area the dealership bodyshops started hiring dedicated painters around the late 1970's. As time went by there were fewer and fewer bodymen/painters. I think now for the most part you are either a professional bodyman or a professional painter.

    I hired into a Cadillac dealer bodyshop as a bodyman around 1980. Everythings going fine for a couple years and all of a sudden the painter just up and quit with no warning. The bodyshop foreman was freaking out so like a dumb ass I told him I would paint until they could find a replacement painter. Things went on for six months and no replacement painter hired. I asked the foreman why he didn't hire another painter. His exact words were " you're the best painter we've had, why would I replace you ?". That pissed me off and I told him I hired in as a bodyman, if I wanted to paint full time I would have hired in as a painter". He just mumbled something and walked away. A couple days later I'm over by the paint booth and a guy walks in near where I was and said he was looking for a job as a painter. I asked him the usual questions about experience etc etc. He seemed qualified to me so I told the guy "see that office door over there ? Go in there and tell the foreman I said if he doesn't hire you on the spot then I quit. Then he'll be out a bodyman and a painter." I was back to doing bodywork the next day. New guy turned out to be a good painter.

    Sorry for rattling on. Some pics of the bad quarter with at least one pic showing the door and the quarter would be good.

  9. #9
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    Very interesting!

    I have done just enough painting and bodywork to realize that: A) you are right, they are each different disciplines and, B), they both require a lot of skill and dedication to master.

    I will definitely get out to the car this weekend and take some pictures of the actual damage I am planning to fix.

    Thank you!

  10. #10
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    I have some pictures of the damage to the quarter. The main deformation is along the top of the rear fender/base of the C-pillar, with a secondary area of damage concentrated on the lower-forward wheel arch. All of the damage is to the outer sheet metal only. I have a factory service manual and checked all the datum dimensions in the back of the car and carefully scrutinized the sheet metal inside the trunk and under the car and found no issues. The rear door is a somewhat dented on the outer skin, but inside looks unaffected and it opens/closes/latches fine. The car slid along a semi-flexible cable barrier for a few feet and the quarter took the brunt of the force, and the door seems to have had a lot of room to push in against the seals, so the damage was light there. However, the leading edge of the quarter at the top of the fender and the bottom of the wheel arch is pushed in relative to the door now, by 3 to 4 mm. In some of the pictures I unclipped the back of the rocker trim just to get a better view.

    There is no rust on the car, so this is purely a "fix bent sheet metal" repair. I hope the pictures are helpful. Please ask any further questions...








  11. #11
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    A few more:






  12. #12
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    Thinking about it a bit more, I am starting to like cutting at the bottom just at the top "edge" of the rocker, as the rocker itself is not damaged, so my welding would be from the top... (the black strip in the picture is the seal for the rocker cover, all of which would be removed of course...). Only the weld seam across the door jamb would be highly visible from a finishing perspective.






    For the upper cut, my choice seems to be to either cut out the entire C-pillar (which will necessitate removing the rear glass) or cut near the base of the C-pillar, just above the most aggressive damage. I am leaning towards this, but am really interested in the views of the experienced!


  13. #13
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    If I were doing it I'd probably cut the bottom cut a little lower so that the seam is behind the rocker cover and on the top I'd cut a little higher so that the seam would have less angles that would need to be dealt with. Otherwise it appears to be a fairly easy job if it has no internal damage.
    Last edited by Len; 07-27-2021 at 11:10 AM.

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