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Old 10-15-2017, 05:53 PM   #1
zaq123
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repairing rust... no experience here

One thing that I will be doing for the first time with this build, is repairing rust. Luckily, this e30 has only one major spot that needs looking into. The area in question - front wheel well seam under the windshield washer tank. I noticed that about 1' of the seem sealer was cracked so I scraped it off. There is about quarter long thru hole into the wheel well but the rest of the seem looks solid, just a surface rust. What do you guys suggest? I was thinking to clean it, weld a small path from the inside of the wheel well, treat the rest of the seam with rust converter, paint and reseal with 3m sealer?

My rebuilt stroker is ready to go in but I would like to address this first while I have the room to work there

Last edited by zaq123; 11-13-2017 at 11:07 AM.
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Old 10-15-2017, 05:58 PM   #2
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A few pics. There is also a rust spot where exhaust manifold was very close to the well. I think that one doesnt look too bad.

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Last edited by zaq123; 10-15-2017 at 06:10 PM.
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Old 10-16-2017, 05:03 PM   #3
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to fix the hole......should i cut it and tack a small flush patch then just fill it in? similar to the attached pic but much smaller patch. I understand that the area is somewhat structural but affected part is pretty small. Or should I clean it up and weld the patch over the hole from underneath the the wheel well? Above pic looks worse that it actually is. The rust in the seam is just a surface rust with the exception the hole area.

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Old 10-16-2017, 07:53 PM   #4
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Maybe you're already aware of this, but the first step prior to actually fixing the hole should be to determine the full extent of the rust. You will want to get down to clean metal all around the hole so you can identify any areas that may be thin, even if they aren't rusted through. Thin spots from surface rust can make it difficult to weld in the new piece since it will be very easy to burn through these areas. I've found a wire wheel on an angle grinder to be a good way to quickly remove rust down to bare metal without too much risk of removing good material (like can happen with a flap wheel). What you find at this stage will inform the way you go about fixing it.

Once you've done that, I would recommend cutting out the thin areas surrounding the hole with a cutoff wheel on an angle grinder. Try to make a rectangular hole so that the patch is easy to fabricate. Since the geometry in this area is pretty simple, I think a flush patch would be a good solution. Make sure to avoid large gaps since these will be annoying to fill without burning through repeatedly. If you're worried about this, an overlapping patch can be used. You may want to weld from both sides to make sure you don't leave any opening for water to get trapped in.

Once the patch is in, the rest of your plan seems good. Rust converter, seam sealer, paint, etc. Make sure all bare metal is treated, and make sure water can't get trapped anywhere.

One final word of caution - rust rarely looks worse than it is. Typically, the wire wheel will expose much more thin material than expected. But hopefully, that will not be the case this time!

Best of luck to you. Let us know how it turns out!
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Old 11-13-2017, 06:08 AM   #5
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Well, I did some repairs, had to cut out a section on the bottom. Could have one smaller section but both folded flanges had rust trapped in between. Cut out the section, primed both flanges, welded patch to the wheel well from both sides and spot welded to the flange on the horizontal panel. Didn't grind to perfect, tough spot to use my grinder and will be covered by sealer anyway.

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Last edited by zaq123; 11-13-2017 at 06:27 AM.
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Old 11-13-2017, 06:29 AM   #6
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Some more pics

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Last edited by zaq123; 11-13-2017 at 07:03 AM.
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Old 11-13-2017, 08:49 AM   #7
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Looks great for having no experience. Great job!
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Old 11-13-2017, 11:19 AM   #8
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Quote:
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Looks great for having no experience. Great job!
thank you.It was a paint to spot weld the whole length of the patch. But I don't know any other alternative as the sheet metal is pretty thing there and to much heat could distort it.

Question about the seam sealer. I cleaned it back long enough where I no longer see any corrosion under it. do I need to remove the entire length of the joint or I can just overlay the old one a little?
Also one thing I learned...a little after the fact: Seam sealer can't go on the self etch primer (the one I used). I don't have epoxy primer available. Should I just paint over the self etch and lay the sealer on top of that? Anyone with any knowledge/experience in this field? Thank you
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Old 11-15-2017, 08:54 AM   #9
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What I do is spray some kind or rust converter between the seam, where you repaired it and also a bit further. Not sure if it's very effective but can't hurt. When applying seam sealer spread it out a bit further so there isn't any gap between the original and new.

I think seam sealer on self etch primer shouldn't be a problem. Were you able to peel it of when it was dry?
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Old 11-15-2017, 09:49 AM   #10
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Quote:
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What I do is spray some kind or rust converter between the seam, where you repaired it and also a bit further. Not sure if it's very effective but can't hurt. When applying seam sealer spread it out a bit further so there isn't any gap between the original and new.

I think seam sealer on self etch primer shouldn't be a problem. Were you able to peel it of when it was dry?
There is no rust left, I cut and cleaned everything and primed bare metal before welding (self etch weld thru primer, gray in the pic). Rust converter won't have any rust to convert. I didn't apply new seam sealer yet. Old one was stuck there good though. I got a can of epoxy primer and going to lay it there after cleaining self etch stuff off. 3M specificly states no self etch below the seam sealer for some reason. Epoxy primer spray can is pretty cool but have to use the whole thing once activated. Probably hit some other spots with it at the same time...like bottom pinch seams by the jacking points. PO of the car bent them so I have to straighten them out and repaint.

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Old 11-16-2017, 11:12 AM   #11
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When I repaired quite a bit of rust on my Touring, I let the epoxy primer seep in between the seams. There's a Youtube video showing weld thru primer vs letting epoxy seep between the seams. The guy explains it pretty good.
https://www.youtube.com/watch?v=SK2CSJRp5js
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Old 11-16-2017, 02:58 PM   #12
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When I repaired quite a bit of rust on my Touring, I let the epoxy primer seep in between the seams. There's a Youtube video showing weld thru primer vs letting epoxy seep between the seams. The guy explains it pretty good.
https://www.youtube.com/watch?v=SK2CSJRp5js
good video. Should I redo it? or should I just spray the epoxy and push it down the seam with the compressed air? I will definitely be removing self etch where the seam sealer will go and spraying epoxy there. I have a test metal strip with the self etch that I soaked in some salt water and left it sitting outside. If there will be any rust on it after a week, I will redo the patch and lay the epoxy in the seam
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Old 11-17-2017, 09:36 AM   #13
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You don't have to redo it, the weld thru primer will protect the metal already a bit, applying the epoxy is just an extra protection. Just apply it thicker around the seam and let it soak in.
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Old 01-12-2018, 06:10 PM   #14
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long overdue update. Self etch test strip hold up to seating in the snow and salt for a month so I decided to leave the patch. I did end up scraping all self etch from the surface where seam sealer contacts. I used 2K epoxy primer on bare metal, 3M Ultrapro seam sealer and painted the engine bay with 2K single stage Alpine White 2 code 218.
It was a pain to match factory messy seam sealer...I tried.
Happy how it tuned out so far. Can't wait to drop freshly assembled 2.9L stroker in there. That engine was sitting for way too long now

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Last edited by zaq123; 01-12-2018 at 07:22 PM.
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Old 01-12-2018, 06:44 PM   #15
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forgot to mention.. if you see any factory seam sealer lifting off and no sight of rust, there is 99.9% chance that you will find plenty of rust hiding behind it.

Last edited by zaq123; 01-12-2018 at 07:27 PM.
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