BMW E30 Battery Box Rust Repair Guide | How To Fix Rear Battery Box Rot With Welding | 016
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- Опубліковано 4 лип 2024
- BMW E30 Battery Box Rust Repair Guide | How To Fix Rear Battery Box Rot With Welding | 016
In this BMW E30 restoration episode, I tackle the typical BMW E30 Rear Battery Box Rust.
This is an absolutely classic place for these old 80s 90s 3 series cars to rust through. Due to the design with the sunroof vent, its inevitable that water ends up getting in the boot, in that box, sitting there for years and eventually rotting through that thin skin of metal.
Here's what I use in this video:
Clarke Weld MIG 150 TE Turbo: ebay.us/jbdfE8 (this is the newer version)
0.8 Welding Wire: ebay.us/eQWqWx
Argon/CO2 Welding Gas & Regulator: ebay.us/7BOngD
Angle Grinder Wire Brushes: ebay.us/sSJjtM
Dewalt Angle Grinder: ebay.us/CmsNuW
Safety Goggles: ebay.us/2Dvt5C
My E30 project is actually a 316i so the battery is situated at the front under the bonnet. The front battery box is also a typical E30 rust spot, but I'll get to that at a later date..
Batteries were situated in the boot for the 6 cylinder cars which is why its referred to as the rear battery box.
.
To tackle this repair I used my trust Clarke welder, some argon/co2 mix welding gas, some 0.8mm mild steel welding wire, and of course some new sheet metal, in 1.2mm to be exact.
I started off by using a wire brush on an angle grinder to clear away the rust and see exactly what needed cutting out. Once the rust was cleared I found an additional small rust hole which I decided to repair while I was there, adding a notch to the top of my cut-out.
I cut the rusty metal out using a cutting disc on an angle grinder, and had to cut the metal in two pieces rather than one neat one. With that removed, I used the old masking tape trick to get a better template of the patch I needed to cut.
I then set about cutting my patch to weld in from the sheet metal. This turns out to be one of the hardest parts of any rust repair, especially when its a more complex shape with multiple bends in it too.
After a lot of back and forth to trim and refine my patch, I did the main bend in the metal using my vice and a hammer to give me a relatively clean and straight bend. I was quite happy with it after all.
As the inner part of the battery box (facing the spare wheel well) was also rusty, I'd cut that out too and opted to weld a new piece on there first, the idea behind that was that I could butt my main patch up to it to reseal the battery box off and prevent future rust.
Once that was welded in and cleaned up with the angle grinder, I moved onto welding in the main part of the repair. Using a couple of handy welding magnets to hold the repair piece in place I set about getting a few tack welds on which was successful.
The method for welding thin sheet metal body work on a car like this is to work around tack welding everything rather than trying to lay down beads. I'm far from a welding expert, but with my Clarke MIG welder set on its second to lowest setting, I was getting good penetration and the tack welds were laying down very nicely.
A pro welder would be able to do this without building up so much weld, but knowing I could come back and clean it all up with the angle grinder later, I set about making sure there were no gaps in my weld.
To top it off, I also welded from the inside to make sure everything was tied in solid from both sides.
Once done, I allowed my welded bodywork to cool down before using a sanding flap disc on my angle grinder to knock all the welds down smooth. I then panel wiped and threw on a coat of primer on to prevent flash rusting in the meantime while I do more work on the E30.
As you can tell from the footage, I'm very pleased with the end result, if I'd paid a bodyshop to do this professionally, and they came back with the same result, I'd be very happy with the job, which is a very good sign.
This rust hole repair success gives me confidence to move forward with the project and take on the next big bodywork issue - the wheel arch.
For more helpful how-to guides and restoration project logs, visit our blog: www.spannerrash.com/
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Done great job I have same problem on my own e30 glad to see what needs done ,got a quote off 800 euro
Cheers! To have it professionally repaired I'm not surprised. It's super time consuming to do.
A Good solid repair with confident welding.
Thank you mate! 😁
@8:30 is why safely glasses were created lol opps
Absolutely! Always pretty darn scary when an angle grinder disc gives up...
@@SPANNERRASH love the videos! Thanks
@@impsquared Cheers! 😁
I want to hit the like button before watching because I'm sure the video is great. Have a nice day pro .
Thanks so much mate, hope you enjoy the vid! :D
Thanks for the video !!
I need to do the same on my E46 and will be inspire from your work
Thank you! Yeah, this is a very common one across many BMWs, I hope the E46 is easy to repair for you. 😃
Great job !
Cheers, this is a common rust issue on E30s glad it's sorted on this one now. 👍
Hi
You are doing a really good job - very interesting
Thanks John, glad you're enjoying the vids. :)
Welding is good. people always go on about a good welder does not grind. I would love to see that. I thought your patch panel was brilliant also. Been welding up cars for 25+ years, never seen that trick with the masking tape. Will be using that.
Thank you for the kind words, Bill. And from a guy who has welded for that many years, that really means a lot! 🥳
Yeah. That usually comes from the guys who work at heavy industry. Welding sheet metal ain't really "welding", just tack tack tack all around. Ive never seen anyone weld a car without grinding the welds down.
Worth getting some cold air on the welds with the compressor between tacks, unless theres a few minutes hidden between each tack you rosk warping panels once you're onto arches etc 👍
I was only leaving a few moments between tacks in this vid to be honest. Probably nowhere near enough as I was getting carried away. :)
I'll be more careful when doing the arches, cheers!
😍😍
Best way to improve, just keep welding, I used to heavy weld 3 runs 5mm thick plate, ended up welding thin gauge steel, used 0.6 wire and low power, biggest problem was the inner liner of the torch, we had to keep blowing it out, we welded so much it was full if powder filling off the wire, we often had to change the liner or torch assembly, we had a prankster who would throw little bits of rubbish under you while you were welding hoping it would catch fire, I welded his tobacco tin to the bench, he nearly broke a finger trying to pick it up, he stopped messing around after that. Just keep welding, strangely the more you weld the better you get.
Cheers Taz, thats a pretty funny story too! 😂 I'm sure there's plenty of welding left to do on this project so I bet I'll improve some.
Why do you suspect it rots just from water being present in that box IF, presumably, it's entirely painted in there without bare metal exposed nor anything abrasive to chip or scuff the paint away? This is something I never understood. Bonnets, roofs, boots, doors largely don't rust because they're painted and not compromised to expose the underlying metal, and they get wet countless times. If anything, the edges of those areas rot because they get nicked and paint is chipped. So someplace like that trunk box, it's a mystery to me.
Your thoughts? Awesome content by the way. Your demeanor is outstanding 👏
Cheers Gregory, and that's a bloody good question, one which I've pondered myself.
Battery boxes are a very common one on all cars due to spillages of battery acid or maybe even the fumes from a battery degrading the water barrier.
Obviously in my case, its a 4-pot E30 so the battery is up front, so it can't be that.
Maybe water just works its way through the coatings over time if it sits for long enough, and in places like this it can sit indefinitely pretty much.
With exterior panels, they get wet, but they also dry much quicker so never stay that way too long.
Or it might be that the rot started externally on the rear box and only when it became a pinhole did it start to rust from the inside too.
Maybe someone who knows the answer can chime in here and enlighten us? 😄
@SPANNER RASH Interesting points you make. Perhaps the paint has some pinholes that are JUST enough to let in the air and moisture. Or perhaps the paint cracked a bit after all the cold and warm changes with the seasons. Is the tail pipe on that side? Might warm the paint over and over there.
Moving on, you also spoke about being careful not to remove the E-coat for fear of allowing rust to begin. 1) how do you visually recognize the e-coat? 2) How do you prevent wearing it away when removing factory undercoating? 3) Why the fear of rust from e-coat removal when you can put the primer on like you do the fresh welded metal?
Sorry to inundate you with questions, but I could talk about these things for hours.
@@gregorymarsh9504 Good points to add also, I can see heat cycles being a factor, paint doesn't last forever in that respect. The exhaust is over the other side though so not such extremes of heat.
1. Ahh yes, the E-coat is quite apparent on this car as a matt grey finish to the metal. When you scuff this with say a heavy wire brush it becomes shiny where the e coat is removed to reveal fresh metal. This freshly exposed metal seems very keen to rust compared to metal finished with an e-coat.
The e coat isn't really like a thick paint, for example it never seems to flake off, but similar to paint it eventually fails and rust creeps from that point of failure.
I'm not totally certain how the e-coat is applied in factory, its possible they dip the chassis in it rather than apply it with a spray.
2. My method so far is to carefully identify where rust is, and focus my efforts on taking these parts down to bare metal and re-coating. And areas where there is no rust I have simply resurfaced the factory underseal to take a fresh layer.
Of course, there are many places I've gone through to bare metal necessarily, but if 75% of the original e-coat remains in place where it's solid, I think I'll be better off than removing it all whether its solid or not.
I think there are some clever ways to remove undearseal coatings without also stripping the e-coat. But they are extremely painstaking and use nasty stripping chemicals.
3. I've found etch primer to be very helpful in protecting bare metal where the e-coat is gone, but its not uncommon for a part to re-rust through the primer after a while if its not given a more robust top coat soon after.
A trick I like to use is give a light coat of etch primer to bare metal, then follow up once dry with a more robust and waterproof epoxy primer to lock it in, then go from there.
At the end of the day, these spray can products will never be as good as the factory coatings so you have to get a bit creative at times.
@@SPANNERRASH Thank you for such a well thought out reply!!
Hi there, great work, what make welder do you use??
Cheers George! Its a Clarke 135, seems like a great welder although discontinued, this is probably the closest one in their lineup now: ebay.us/jbdfE8
@@SPANNERRASH Thanks, will try and get one👍
Try using a multi tool on the seam/under sealer, it scrapes off easily with that mate! 👍🏼
Cheers! I saw that technique very recently, its a genius way to do it, I should pick myself one of those tools up. :)
I only just saw it too, on bad e30’s channel 🙈👍🏼
Thanks for the content, just finished this weekend same pocket on mine. Next will be left rear fender and jack points.. then hopefully will be finished after 6 months of rust issues..
What is coming next rust wise, almost finished?
Awesome, hope your rear compartment repair came out as well as mine did. :)
Just like you, I need to start turning my attention to the rear wheel arches.
It looks like there's some rust on the inner passenger arch, and of course the big hole on the drivers side inner and outer.
I'm quite intimidated by that job still as it's an important part of the car for all to see.
I've ordered repair panels for this as I've realised there's absolutely no way I will be able to shape my own.
Probably for the best anyway, they are cheap enough on ebay. :)
@@SPANNERRASH I had also used a replacement panel for the driver side. It is hard to replicate, sure..
I have first done the exterior panel on mine and then the interior by shapes.
Exterior panel goes well on superposition. Non need to be worried on this.
For the interior panel, i had to shape a piece because I didn't found one. The trick i used here is to give it a raw shape with masking tape 4 5 layers. Then starting tack welding it in on extremities with a hammer to give it the shape as it goes. Also a hummer and big flat screwdriver for closing gaps in between welds helps a lot.
I would say, it is the one spot that takes the longer, but on mine I had to replace nearly 180°. So i think it will be easier for you.
Hopes you the best.
@@Muraatdeekur Thanks mate, thats really encouraging.
I'm sure I will try your technique of shaping the internal panel with a hammer as I go.
@@SPANNERRASH Today I started passenger side rear arch.
I tryed to keep the rusty piece as much in shape as possible. Same idea as in your video to use the cutted piece as a template. I had a very good fitment so thanks to you.
I will try to weld it in place with even better fitment thankfully with the hammer technic lol.
If only I would have got all those little tips at the beginning.... no regret still but would have taken less time for sure.
@@Muraatdeekur Awesome sounds like you're making great progress, and I'm really glad the template technique worked for you.