Winter Project Advice

[floatinghead]

I bought an '82 320is about 2 years ago that was in running, but in pretty rough shape. I've done some basics to get it going and still have more to do to get it in a solid, reliable place, so the plan was to take care of some big ticket items this winter. The primary issue is rust in the frame rail below the brake master. I poked around and it was good toward the front and back from that spot. Floors looked like they were patched before and i'm sure there will be some stuff around the battery tray as well. The passenger side is solid and aside from tire wheel well and a few spots on trunk lid, thats about it ( famous last words).

So my question is: If i remove brake master/ booster and all other accessory stuff in that area, would i be able to make this repair by dropping the subframe and keeping the engine in place? Or would it just be too tight to do that work. I'm trying to get a sense for the scope of the work as well as where i'm going to put parts/pieces while i work in my cramped garage. If the engine needs to come out, then i'm sure there's more that i would do ( clutch, shifter stuff, driveshaft....)

A lot of this stuff is new to me, but I did a subframe refresh + engine mount repair on my 2002 last year, so i'm working up the courage to do more. Below is a shot of the area that needs the most attention.

thanks,

Baron

[mjweimer]

Seems like a reasonable course of action for that repair. You might want to also drop the strut assembly on the drivers side to allow for some more wiggle room.

I think the hardest part will be dealing with the two layers of metal in that area...this is the section where the front frame "horn" overlaps the stub on the unibody. The plug welds secure the outer metal to the inner metal (forgive me if you know this). If the damage is only on the bottom of that section, you might be able to grind out all of the rust and stitch weld a plate over the area. Use of a weldable primer over bare metal, paint and seam sealing of any gaps in the patch panels should make it a long lasting repair. You can also get body cavity wax from 3M or Eastwood that has a long wand...you can coat the inside of the frame rail after it is repaired through the hole near the rear brake line.

Keep us posted.


MJ

[floatinghead]

mjweimer, Thanks for your response. The two layers was what i was curious about as well. It looks like it rusted from the top side through the bottom, so I want to make sure there's enough metal to keep it all together! I wasn't sure if the top layer could be fully removed or how how the panel is? Does it run all the way to the nose? Or would it be best to cut back enough to expose the inner layer then repair the inside and then outside. I probably need some more time poking around, but there's a lot of stuff in the way to get a good picture of what needs work. here are two more shots of the area. All advice welcome!

Screen Shot 2020-10-26 at 7.45.05 AM.jpgScreen Shot 2020-10-26 at 7.44.31 AM.jpgScreen Shot 2020-10-26 at 7.44.00 AM.jpg

[dukedkt442]

I have a spare drivers floor and spare tire patch panel, along with front fenders, I'm holding on to as I kick my project down the road. Feel free to reach out if you end up needing them.

[mjweimer]

mjweimer, Thanks for your response. The two layers was what i was curious about as well. It looks like it rusted from the top side through the bottom, so I want to make sure there's enough metal to keep it all together! I wasn't sure if the top layer could be fully removed or how how the panel is? Does it run all the way to the nose? Or would it be best to cut back enough to expose the inner layer then repair the inside and then outside. I probably need some more time poking around, but there's a lot of stuff in the way to get a good picture of what needs work. here are two more shots of the area. All advice welcome!

Screen Shot 2020-10-26 at 7.45.05 AM.jpgScreen Shot 2020-10-26 at 7.44.31 AM.jpgScreen Shot 2020-10-26 at 7.44.00 AM.jpg

Yes, that outer material runs from that point all the way to the front, it would be a major task to remove the whole piece. Look at the last picture in this link to see how it integrates with the inner fender and front radiator support:

https://prussianmotors.com/1977-1979...nel-oem-22222/


I think you have two paths to effect a good repair and it depends on how much damage there is once you get poking around at the rust holes. You could remove the outer panel section in this area, repair the inner and replicate the outer section or cut out and mitigate/cut the rot in the areas and plate over the entire area, top/bottom/side with appropriate pieces. I would make the top and bottom plates a bit longer than the area and run a full perimeter weld (if you have enough access....otherwise do some stitch or plug welds and seam seal).

Option #2 could be easier and stronger if well thought out...I'd need eyes on it to get a better feel for what is needed. Your best bet is to dive in, get stuff out of the way and see what is really going on and how much room you have.


MJ

[floatinghead]

MJ, I was digging around some posts trying to see how these panels really come together, but didn't realize the tie in at the front. I found this post which shows how the frame rail under the floors comes up and then the part that i'm concerned about goes over. Its a good progression if you can look around the broken photobucket links!

https://www.bimmerforums.com/forum/s...pair-E21/page4

Based on this, my first thought was option 1, cut out the first layer enough to repair the 2nd layer and then patch it back up. But I think, as you mentioned, it will come down to how much rust is in that area. I need to inspect forward from that area to make sure it really isn't that whole section, though i know there's stuff around the battery tray, but it looks more surface and not structural. If I did option 2 and prepped well, used cavity wax on the inside and weld thru primer and seal sealer it would last?

I'm thinking that taking out the engine/transmission might be the best path to ensure enough room to do the job correctly. But I would start by removing all things on drivers side first to see what access I can get. I'm not looking for anything other than a driver ( as the paint and body are dinged up enough already), but want to make a nice clean repair that will last. Plus i'm doing this to learn on. This has me freaked out a bit as its a bigger job than anything i've done in the past, but it would be awesome to say that i did it....

Seems like it's time to make a real plan.

[mjweimer]

That's a good post and shows some really good detail of how it all goes together.

I think the repair would last a long time if you were able to get most of the bad rust out and then prepare and treat what is left before you cover it up. In that post it looks like he was priming the panels before welding and then welding and painting the outside....no mention of the inside. Using that same method would only leave the metal exposed from the weld penetration/heat on the inside...topping it off with the final step of cavity wax should seal up the exposed areas really well.

I have done some similar repairs on an E30 with success...obviously not as good as a virgin E-coated chassis but it's about the best you can do to get it all to last. I used weld-through primer as well as a product called Fertan to treat remaining surface rust before painting. Part of my repair was very visible in the engine bay so I purchased a can of 2K epoxy primer to seal up the cleaned up surface and then 2K paint to match body color. You might not need to go that far underneath but paint in the 2K can is essentially the same as shooting from a pro gun and you can buy it in a basic black color.

https://www.amazon.com/FERTAN-22220-...2PS0MVGQ6CJDB6

https://www.66autocolor.com/Spray-Ma...pm-3680001.htm

https://www.66autocolor.com/SPM-3680...3680032-34.htm

https://www.66autocolor.com/Auto-Spr...mixedpaint.htm


Good call on pulling the easy stuff to see how much room you have and making a solid plan. As with anything, using the right methods and materials makes the difference in a great or not so great repair. Prior to the E30, I had never done anything quite this involved and so far it still looks as good as the day I finished.


MJ

[floatinghead]

Thank you for the links. I'll keep you posted as things progress!

Baron

[floatinghead]

Finally have the e21 in the garage and about ready to start removing stuff for frame rail repair. My original plan was to remove stuff in the area, leave engine in place as I'm a bit short on garage space and then fix the repair.

1. If I do leave the engine (supported from the top fenders likely) and remove the subframe, will the body be strong enough to support the engine while i start to remove the rusty areas? Anyone done a repair like this with engine in?
2. Or should i really start planning an engine/trans removal and try and figure out where to put all this stuff? I've never pulled an engine or trans, but willing to take it on.

thanks,

Baron