Replacing Underbody Panels

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by Valiant V, Jun 30, 2021.

  1. Valiant V

    Valiant V Member

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    On our first long trip in our new-to-us 2017 Prius (Three), I notices a "fluttering" or buzzing sound above about 60 mph that varied a bit with speed and the bouncing of the car over waves in the road. It appeared to be coming from around the driver's door. Stopping to check it out and finding nothing at first, I finally traced it to a loose panel under the car - between the left front wheel and the "bumper" (front air dam). I was able to snap it back into place and all was well - until about halfway through our second long trip, where I heard a scraping sound getting off the interstate. Sounded something like a brake disk shield.

    Turns out this same panel - a roughly triangular piece of plastic maybe 10" or so on a side - had come loose again and was now scraping on the ground. Being a little smaller now (due to being dragged against the pavement for perhaps 100 miles) it didn't snap back onto place. I was able to tie it back into position with a zip tie.

    At any rate, I'd like to replace this piece and do a proper repair - and fill in the whole area again - but from what I could find online - it looks like this piece is only sold with a whole fender liner/splash guard/wheel well/ whateveryoucall it. I found it online for ~$72 buck (plus shipping of who knows what) but I was wondering if anybody else knew if the part I'm looking for is available by itself.

    Near as I can tell, this is the whole part:


    2017 Toyota Prius Prime Fender Splash Shield (Left, Front). Interior, HOOD, Body, Radiator - 5387647140 | Serra Toyota, Decatur AL


    The piece is relatively flat, I could could likely fabricate one, but it would be nice to have the "right" piece there. I'll have to get the car up on ramps to inspect further as It looks like other similar parts under the front of the car have similar damage.

    I would guess that the very-low front end has had a few encounters with curbs, or dips in the road from the scuffs on the bottom of the front air dam - and that broke something loose to start the process of this piece coming off and getting further damaged.
     
  2. Georgina Rudkus

    Georgina Rudkus Senior Member

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    As I recall, Toyota uses 7mm nylon plastic push in rivets. M5 rivet nuts fit this hole perfectly without enlargement.

    If you prefer to enlarge the holes, they can take M6 rivet nuts and M6 flange bolts.

    To prevent the holes from tearing through the polyethylene plastic, I recommend and personally use large 1/4 inch fender washers with neoprene linings, which I purchased off of Amazon.

     
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  3. Valiant V

    Valiant V Member

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    Good to know - but since I haven't managed to source the actual panel itself - I haven't even gotten around how to fasten it on.

    It looks like it attaches to adjacent panels with the push-nuts or plastic rivet thingies.
     
  4. Georgina Rudkus

    Georgina Rudkus Senior Member

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    More stainless steel neoprene fender washer alternatives that will fit M6 fasteners.



     
  5. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Looks sim to 3rd gen. It "looks" like it could be two pieces, and the arched bit and flat back bit likely could be separated, when new. 3rd gen has a slim flat-bar piece at the junction, and 3 bolts going into tack-welded nuts on the flat-bar, at the junction. When I tried to back out those bolts with our 2010, a few years past new, I snapped the heads off (twice, then gave up). The bolts/nut junctions looked like they'd been at the bottom of the sea for a while.

    Oh and on 3rd gen, there was one fastener at the very rear that pretty much has to be destroyed to remove.
     
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  6. Valiant V

    Valiant V Member

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    I suppose if it really is one piece, then I'll have to fabricate a replacement on my own as I don't feel like spending $75 plus high shipping (bulky part) for something that also looks like a real PIA to replace.
     
  7. Mendel Leisk

    Mendel Leisk Sand Pounder

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    It ships folded up IIRC, fairly thin material. Start a check-out process and see what it amounts to, to know for sure. If you bail they’ll likely send you an (automated) email, saying “did you forget something?”, no big deal. Research the fasteners too (for any MIA); I’d go with the Toyota, just my 2 cents.

    if you do order fasteners, remove the damaged one first, to make completely sure which you’ll need: again, there’s one that may need to be destroyed to get off.
     
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  8. gene

    gene Member

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    What did you end up doing? I’m in the same boat. About $85 shipped for the whole assembly (The cost is no biggie, so hate to buy and ship more plastic I don’t need), when I just need the triangular part—which is clearly a separate piece since I have it in front of me.

    The main problem is that one of the corner pieces tore (see photo) and I’m not sure I can re-fasten it in a way it will stay on. I’m wondering if there is a set of washers with “teeth” that I can use to re-attach this corner. image.jpg
     
  9. Georgina Rudkus

    Georgina Rudkus Senior Member

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    Get rid of the small piece that broke off and use these #14 x 1" Neoprene EPDM Bonded Sealing Washers, Stainless Steel.




    For additional stability, one can bond the neoprene portion to the contact point of the undercover with a high strength contact cement, epoxy or 3M VHB tape.

    I use them to prevent the little piece from breaking off in the first place, The neoprene washer spreads the contact over a larger surface area.
     
    #9 Georgina Rudkus, Oct 22, 2021
    Last edited: Oct 22, 2021
  10. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I would first put that broken off piece back in position, with 2-part epoxy in the joint, and beyond. Let that cure, then sandwich the area with a folded-over piece of fiberglass mesh (designed for bridging gaps, strengthening), covering the whole area, including and beyond the hole, and apply more 2-part epoxy.

    When fully cured, drill a hole through the patch, at the original location and diameter. Maybe start with a 1/8" pilot hole, then (if possible) forstener bit drill from both sides with a drill press.
     
    #10 Mendel Leisk, Oct 22, 2021
    Last edited: Oct 22, 2021
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  11. vvillovv

    vvillovv Senior Member

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  12. thomassster

    thomassster Member

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    If it’s just that corner, there are videos in YouTube that show how to weld/solder with a very cheap soldering gun and some plastic scrape and cheap mesh. Most epoxies I’ve tried are still too weak and are prone for breakage again.
     
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  13. gene

    gene Member

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    Yes, I actually came across soldering for plastic repair which I had not thought of. I have a 4hr drive today and don’t have my soldering gun with me, but will give that a shot when I’m home. For the drive today, hopefully the fender washers I was able to get locally (not as large as I’d like) will hold well enough (seems like it should be good enough for one trip).

    It seems we also lost two of the three plastic clips, so I’ll need to check this and a couple other threads for replacement options (I think I saw a couple mentioned).
     
  14. vvillovv

    vvillovv Senior Member

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    If you pull the clips you're missing from the other side of the car and post a picture with a dime or quarter next to them, someone will find the right part number for you.
     
  15. Mendel Leisk

    Mendel Leisk Sand Pounder

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  16. gene

    gene Member

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    I actually found that:

    Genuine OEM Toyota Parts and Accessories Online - Toyota Parts Deal

    Has good prices and much more reasonable shipping costs on larger parts than I found on McGeorge (who I have used before). Pretty sure I know which plastic clips I need, but pay try to use something a bit more durable, especially since I think at least one of the two holes stripped a bit when they were ripped out.
     
  17. Mendel Leisk

    Mendel Leisk Sand Pounder

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    A tip for plastic fasteners, typically the ones with the centers you need to pry up: ALWAYS wash them out with hot soapy water when they've been removed, and work the mechanism back/forth a bit. And be careful installing them: be sure all the little jaws are squeezed together, go into the hole.

    A paint can opener tool is handy for prying them out:

    upload_2021-10-24_7-58-47.png
     
  18. Colorado Boo

    Colorado Boo Member

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    I hate those plastic attachments manufacturers use because there's so many different types and sizes. I have a bunch of boxes of various sizes I got off Amazon in my garage and have to search through them to find one that will fit those that are missing or damaged when working on vehicles. And, in the rare instance where I can't get one to fit, a zip-tie is my last resort. (But that's pretty rare, I'm getting pretty good at preserving the old ones when taking them off.)
     
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