How to Repair Rocker Panel Rust (Mazda Miata Mx-5)
UPDATE: So 4+ years later this quick repair appears exactly the same. The car has seen plenty of miles, salt, and track time with no ill effects. Obviously, if you have a nice/valuable car go get it professionally repaired but I've been busy enjoying this crappy Miata!
Let's fix my beater Miata. Keep in mind this car cost $1000, so no this isn't a professional repair. However, this video should guide you through the basic process of repairing rusty rocker panels (or sills) on a NA Mazda Miata (Mx-5) or similar vehicles.
Disclaimer: Remember, I'm just a guy in a garage that likes to mess with cars...not a trained professional. Use tools and this guide at your own risk. Due to factors beyond my control, no information contained in this video shall create any expressed or implied warranty or guarantee of any particular result. Any injury, damage, or loss that may result from improper use of these tools, equipment, or from the information contained in this video is the sole responsibility of the user.
Everything was on point until the painting part. I wish that came out nicer.
Awesome video! My dream car is a ‘60s-‘70s Opel GT, and I have been trying to get one for many years. Almost every one I’ve seen has rust in the exact same spots, and I’ve always been worried about having to do rust repair and body work. This video, compared to a lot others I’ve seen, makes the job look pretty straight-forward and somewhat easy! Thank you so much!
I just bought my 92 and love it. Then I found a golfball sized hole right where yours is and I'm devastated!
all my rockers got a golfball size whole atleast,will appreciate the guide here to repair!
Too bad it started snowing at 10:40. - But he stays focused and keeps working, so I'm confident this will turn out great!
LOL
Don Fisher said
I’m assuming that was a joke because that was the substance he was sanding not snow
Thanks for the video. Couple of comments,. the Miata and MX5 range rear sill corners generally always need repairing to the inner sill as well. For those not familiar, the water accumulates there because the escape drip holes from the rear shelf where rain runs off the hood get blocked. The only real solution is keep them clear, poke them through with some curtain wire,. it will exit at the sill if the hole is free of dirt. When repairing, once the outer sill is cut away cut the inner section out as well and weld in the new metal areas. A few small speaker magnets will help keep the metal parts in place when welding. Hope this helps too !
I have a 1990 that I was afraid of peeling away the rust. After watching this video, and knowing that I have less rest than what you had, makes me confident that it's not as bad as I'm worrying. Thank you for the video, it's incredibly helpful.
On paper the Mk1 Miata shouldn’t be any worse in the rust department than any other car of its era. Later models of the Miata are the real deal when it comes to rust. While the Mk1 Miata just has a normal chassis, for newer models of the Miata it’s a whole other system. Instead of a standard unibody construction, newer Miata models sport double skinned chassis legs. But why? The reason they were made this way is to improve crash safety. Sure, some of them have been destroyed in accidents which left owners owing the fact that they lived to swap insurance details to the chassis construction, but others are still there with their engines purring like a kitten just like they did when they were new. However, one thing is amiss. Water has collected in the double skinned chassis legs and this unchecked moisture is now catching up with the vehicle and its owner, especially in cooler climates where salt is applied to roads in the winter to reduce ice. Now rust is rotting the chassis legs from the inside out. For many, this ultimately leads to the premature demise of the vehicle. However, for those who know how to weld, all is not lost. Just remember to disconnect the battery cables before you start welding, otherwise you might ruin the electronics.
Good guide, however depending on the place you live it's worth to apply some epoxy primer on bare steel before you're using filler. The filler tends to get moisture from the air, where you're having some holes left after welding. But any way great job!
Great video and I will be doing this same repair shortly, only thing to add is make sure the battery is disconnected to avoid frying the ECU when welding.
This repair is much better than most rust repair videos on youtube. Nice work
Thanks for the upload! Will use this while reparing my Nissan Skyline. Both sills and rocker-panels! Will make a video and show you the result!
wow. thanks for uploading this video. this is gonna help me on my future project.
You've given me hope that I might save my little Miata yet. It's a losing battle up here in the North, even without driving it in the winter.
Good luck! Make sure to clear the drain holes...might help avoid having trapped water in the panel.
True. I'm feeling the same way.
Same here in the UK 1 bad summer car gone 😂
Thank you for this. I was halfway through this job and started to get discouraged on finishing it up, but this video showed me exactly the steps I needed to take. Thanks a million
My first ever seeing a panel replaced.... You made it look so easy!
I loved this video. It is really what I needed to be able to fix this stuff myself. Thank you!
I have a '72 VW Karmann Ghia I'm going to start restoring soon. Base on my preliminary assessment, I think I have my work cut out for me. Your video will go a long way to help me during the restoration process. Thank you.
Very helpful guide! Thank you for this! I will be attempting this myself on my '95 NA I just purchased
you make it look so easy. great job and thanks for the diy video
I will be doing this to my miata; thank you for the great tutorial.
fair do's that is a fairly useful video for all similar repairs covers the basics very well I thought. I'm no professional at repair work but this definitely helps with the basics to get started thanks for the upload
4:04 perfectly timed chisel punch
wow. this is like the only video that shows you how to stop the inside from rusting with weld thru primer. All these other videos just patch things up and leave bare metal on the back like it's never going to rust again. lol.
So thankful for this video. It will definitely help me this summer on my car.
Good luck!
Excellent video, you should do more.
Good job. The rocker panel is on the bottom of the car body. Whenever a car gets wet the water runs off at the bottom of any car or truck. Chances are that all cars or trucks with metal on the bottom of the vehicle is eventually going to rust sooner or later. Your technique is a really good one. It saves a lot of time as well. I think that replacing the entire rocker panel usually is not necessary because rust usually shows up in the same place most of the time. Your technique repairs only the part of the rocker panel that actually does rust.
Great video, Very helpful Not to worried about having a go on mine now Thanks
If your not an instructor, you should be. One of the best how to vids I've seen. Thanks for posting
Very effective and proper repair, very good stuff 👌🏻
Great video, made it look so easy. Can I do this with my harbor frieght flux welder and hours of patience? Or is a lost battle without gas
I'm enjoying watching your good video. I support you in Korea.
카앤맨도 잘 보고 있습니다!
He was nice to see that you actually used the proper drill bit that a lot of people will not spend the money on and I agree with everybody else if you live where it snows fiberglass would have been better
This is def gonna help with our new miata project!
Great video,how did you go about losing the welding line(top)where the repair section joins the rear quarter panel ?.....Many Thanks 👍🏻
Nice work. Looking forward to do the came on my e36
i think you are the only guy who did a BACK SIDE rust prevention . i really never understood why people are welding the panels without care of the back side. but my concern is : when you weld you do not remove some of this material from the back side leaving the metal exposed ? (the mig welds DO penetrate the metal from the front till the back side , heating the back side and removing all the layer of protection from the back side. if it is a blind patch repair we can not spray primer TO the back side , no access..)
Yeah I had the same concern. Not a lot you can do when there isn't access. The alternative would be to replace the entire panel affected and only do spot welds like the factory.
Thanks for sharing this video very helpful. By the way, if I will use POR 15 can I apply bondo to it?
great video m8.my only but is, u make it look easy. when it's a difficult job welding rusty cars.at what point would u think this cars had it, or do u believe they can all be fixed.time and money obviously. considered thanks
Beautiful repair man...very well done
As a non professional, self taught, plenty of experience now on my own project car, all I can say is spray back of new panel/plate with weld through primer, butt weld using MIG, and stitch weld the whole seem, coat in fibre glass resin as it is water proof, unlike sandable polyester filler, then the filler, sand, primer, top coat. I then spray cavity wax on the inside of the panels/sill. I've found any tiny pinholes in the welding, lets moisture through from the inside, which causes the polyester filler to expand and bubble, result job is ruined visually. All fun when it goes well.
Kernow Forest, very good advice! I could not have said it better myself. Tom
Fiberglas is the material, matt , chopped strand or woven. The two resins are polyester and epoxy, epoxy being the best for catch ( grab ) on metal and is not pervious to water like polyester resin. Epoxy has fillers that can be added like bubbles I think it's called but talc works well too. I like to paint on some epoxy and wait until it gets tacky then add epoxy filler so that it all bonds good together. Your pretty much spot on though.
Excellent advice. Thanks and I’ve seen that exact scenario. I lean towards coating the back of the repair area with epoxy primer if at all possible
Thanks for the up load, when can i drop mine off?
Great video bud, very well done and helpful. The music getting loud everytime it switched to you working killed me though lol maybe future videos you keep the music volume low like when your speaking! Keep up the good work and thanks for the share.
GREAT VIDEO my only suggestion is that you use a fiberglass filler next time because its waterproof and its the correct filler to use on the bottom of the car to protect from future rust. and for someone who is doing an oem, finsih use a 2k primer and then wetsand and paint. thanks for the video.
Exactly what I used, did a great job! 2 years later and still no rust on the last area I did. I'll be using the same technique and fibreglass filler on this new area of rust that's appeared.
Isn't the rocker panel structural, though? As such, replacing with fiberglass would present a safety hazard, or so I am told. I thought welding new metal -- as OP has done -- was the only way to (correctly) deal with this type of repair.
Baddest Burrito they are speaking of fiberglass filler as a substitute for the green filler he used, the metal would still be welded on
Ok. Thanks.
2k nwver for me
Excellent. Thats what i call an honest ,no bullshit,repair.
Thanks! hope it helps
What?! In my opinion he should have replaced the inner panel aswell. The rust will come back very soon as it's rusty inside :/
Jakub Doulan he treated it with POR15. Its not coming back
Mazda steel is rubbish
Excellent video!! Extremely helpful! Just subbed!
Hi NeedMoar, great video. I'm wondering if you did any work like this on the floorboards in the cabin. I just found surface rust and also a small through hole in my new-to-me NC, near the outer front seat mount. The hole is small enough right now that I was told JB Weld might be an option, and then grind and prep and apply POR-15. And yes, the drains had been backed up; already cleaned them with a trombone brush.
Excellent job, keep it up.
Ryan Ramsey Thanks!
Hi! Thanks for a great video! Hopefully you are still available since it was posted some time ago but I have a question. I only need to paint the black rocker panels. They are in pretty good condition but definitely need a painting to freshen them up. What is the correct paint, brand, finish etc to match the OEM? I don't need any repairs or primer, just a thin layer or two to bring it back to New. Thanks again for your help here!
Great video. Keep it up!
Thanks. I just found a rust spot on the door of my e38. Will be hitting in in a few weeks.
nice job. what textured paint are you using from 11.21 minute mark ?
Been putting off this repair for awhile on mine. Happy I found this vid
there is original paint from factory? i mean the old paint. nice job thank you
Great work you are an expert
Great video and knowledgeable instructions. Personally, the music blaring in and out was really annoying.
the repair is explained nicely. what wire diameter you were using for the welding (in mm Please)?
Perfect repair, this is the right repair 👍
awesome guide.. makes me feel like I could tackle this project instead of paying some over priced shop for both sides..
Great job !!!
awesome man thanks and clean work!!
Excellent starter guide.
Looks lovely well done
Just bought a 91 gmc that could use this. Didn't know until I brought it home because it has a patch panel and looks good. Inspection from underneath and it could use some touching up.
I'm stuggling a bit with the texture on the paint. Want to do this job myself as well, but what's the correct sequence of actions? stone chip paint is rubbery and has texture, so I suppose this should not be sanded? However, afterwards you apply primer, base and clear coat where sanding is normally needed. Doesn't this then cancel the texture effect?
that really gave me some confidence to want to do this, thank you!! also is that the waterford hills track?😂
Very informative video, Good work but I have to agree with the other posters, only one video? what's up with that? you have knowledge and talent, share LOL More explanation of the welder would be nice but no complaints here. I'd like to offer my truck for you to do another video, I'll hold the camera. LMAO.
Haha I know...got busy with a job change requiring lots of travel. Working on filming an engine build now...
how it should be done ,very nice repair...
Great job. A real repair rather than a cover up. How many hours did this take in general. Thanks
A very common area for rust, I have to do mine now.
Could you tell us what paint cans you used? I have a black one too, and I want it to come out looking like yours. Did you use the Rustoleum Textured Black and then the regular Rustoleum gloss black?
Complimenti per il tuo lavoro 😀✌️
Dankeschön für das interessante Video
hey! Just started working on my own NA, a lot less sever than this rust, so far. Do you wear any eye protection for those sparks? Are normal clear safety goggles okay, or should I have something like a welder's mask?
Sheet metal - 18 gauge weld-thru primer POR-15 or similar rust inhibitor body filler sand paper 80, 120, 220, 320
Very good explanation
Awesome fabulous work
Subscribed! I am from UK , i am struggling to find that metal. Could you tell me what material and what is it called ? Thanks
Nice job 👍🏻
What top coat is that for brilliant black? Unsure of what to use. I’m already using SEM satin as a first layer but I’m pretty sure I need to add that gloss after.
Thanks very much, great tips!
mate, thats one good repair!
Thanks for your Miata Specific video.
Its satisfying i love your videos
great video and very clear..although those are lap welds not butt welds...good job !
Assuming you were doing a patch panel on a quarter panel. How could someone seal the back of the butt weld? I've heard weld through primer doesn't work very well and I'd like to rust proof as much as possible.
Very good your job. From Brazil.
Well done ! Thanks
I'd have loved to see how much faster you could weld with an everlast pulse mig welder. I haven't seen too many videos on pulse mig and sheet metal.
great job looks awesome
Great work
What a great video
Great video! Will be trying to tackle this soon. I can't find a good textured rocker paint that matches the OEM paint, what did you use?
+Liconhomie Thanks! I believe I used SEM #39853. It was hard to find something locally but textured paints are pretty easy to get online. If you are outside the US I'm not sure what's available.
+NeedMoarGarage Thank you! I just re-watched the video to get all the supplies I need, and two questions- what top coat did you put on over the chip guard? I just want to match the rest of the rocker panel, OEM finish. Secondly, will JB-weld work instead of actual welding? (www.amazon.com/J-B-Weld-8265S-Original-Reinforced/dp/B0006O1ICE) I can't weld, and would have to pay a shop to do it.
+Liconhomie I used a single stage paint mixed by a local body supply store. The brand was Nason and they just mixed it by using the car's paint code. I chose to get it in a spray can for simplicity. You could get separate base and clear which might give you better results; most paint supply shops should have either option. I don't think JB weld would do great in place of actual welding, but it would probably be better than fiber-glassing over the rust holes like some people suggest. Once you grind/sand the JB weld joint down smooth, there really won't be much epoxy holding the panel on, and I can see that failing not far down the road. You might consider doing all the prep work yourself, making a good patch panel, and just paying someone to weld it up. The actual welding took me about a half hour.
Great guide, but how did you shape your patch panel? It fits really nicely.
dont know how he did it specifically, but my guess is table edge or some cylinder household item, 18-16 gauge steel shouldnt be too hard to shape into something you like
Great video! Really useful, do you think you would make a tutorial on welding in the future? And also some explanation as to how to size up and fit the new sheet metal? You can tell i'm a complete newbie! aha
+Craf - T I could probably do that on a future project. There are lots of helpful welding videos here on KZhead...I learned from those. Look for a good video on setting up a welder for thin sheet metal, and then maybe others on plug welding and butt welding. Also welder manufacturers have some really good resources on their websites. To size up a patch panel I usually make a template using the side of a cereal box. You can cut it with scissors and bend it to get things just right. Then, you can trace your pattern on to sheet metal. It's simple but will get you really close. Hope that helps!
That's really useful! Thanks man!
Nice work
Wear glove when you use grinder. overall great job !
when I ran out of cake frosting I used body filler for my late husband's birthday cakes!
Thanks! Great video -
How do you shape the patch panels correctly? That’s the part I’m most worried about.
Nice vid man!