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Trunk panel rust hole. Need advice on how to patch it...


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I'm in the midst of restoring the trunk in my '65 Rivi. This car is my daily driver, runs great but has some interior issues that were neglected by previous owners that need attention.

I have spent the last few days with a powered wire brush cleaning off the trunk panels, brushing off the adhesed foam, smoothing out the scratched paint, and chipping off a bunch of filler that some one did a hack job lining all the seems with.

So far so good the only major issue I have come across is in the photo. Two spots of corrosion. I have not come across any major rust other than surface rust anywhere else on the vehicle. My plan is to patch these two holes with fiberglass. I have ground down the rust back as far as I can but one of the holes, most of the corrosion is between the trunk panel and whatever panel is underneath it and hard to get to.

I welcome any and all advice from any of you who have experience dealing with this sort of thing and if any one recommends a particular fiberglass kit. I think the most suitable one I can find so far is the Bondo Fiberglass Resin Jelly Kit:

http://bondo.com/431-bondo-fiberglass-resin-jelly-kit.html

My plan is to re-carpet and re-cardboard the trunk so these panels will not be visible but I'm going to primer them to hopefully curb any further corrosion.

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My first thought when I read "whatever panel is underneath" is that panel is actually the top of the gas tank. Use extreme caution if it is.

Good point and I will, although I don't think it is. The reason why is hard to explain and impossible to get a photo of but it seems that what is under the hole is some kind of cavity and doesn't just open up to underneath the chassis. The reason being is that absolutely no daylight comes through and as far as I can stick my finger in there it seems to be an enclosed cavity of panels.

I'll try to get a better shot of it tomorrow in the daylight and post another.

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There are braces on either side of the trunk underneath. These are close to each wheel well, so kind of in the top right and left cornet of the trunk with the gas tank being smack dab in the middle. As to the fiberglass or what to use to patch it - i bought a trunk kit from eastwood full of por 15 products. In the kit you have por 15, metal prep, degreaser, fiberglass, and a 2 part filler for smaller holes. I would probably recommend the 2 part filler for the holes in your picture. Also, why would someone purchase a trunk panel for 400 bucks when you can buy brand new sheet metal ready to weld in for 250 dollars or thereabouts?

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I think what you're looking at is the part of the trunk floor that is right next to the inner fender. If it is, there's a 'cup' under that section. That cup houses the cage nut for the body bolt. Poor design on Buick's part. The cup gather's dust, the dust gathers moisture, and for some reason the rust appears on the top.

It will take some searching but someone on the forum ordered a cup for a Camaro or Chevelle and welded it in. They did a good job and the replacement part worked well.

You could also have a broken rear window seal, even more common. Water sits in the bottom corners of the glass channel and as it get dirty it eventually corrodes the metal and allows water to leak into the trunk in the same area that I described above. That will require the removal of the rear glass, removal of all of the rusty metal, and forming and replacing some new metal to replace it.

Either way, it's not uncommon and you can find threads on the subject by doing a search.

Ed

Edited by RivNut (see edit history)
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I am finishing up my trunk at the moment from damage caused exactly as you described it. Back window seal failed...water got in the trunk and wrecked things. I had to replace some of the passenger side support with some 14-16 gauge metal it was so bad. I will be furnishing pics after i complete the repairs sometime this month. One more trunk patch then i am cleaning and prepping to lay down the por 15 silver from the front toe boards to the back of the trunk in one fell swoop, or at least that is the master plan.

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post-98277-143142798185_thumb.jpg

I could tell just by looking at my rear window prior to pulling it. Just like every other bit of rust i assumed what i could see was just the tip of the iceberg and i wasn't wrong. these pics were done from the back seat looking towards the rear of the car along the shelf.

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Edited by devildog93 (see edit history)
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Kaber,

Thanks for that. Those photos help a lot in knowing exactly what it is that I can't see. Still going to try to patch it with fiberglass but now I'm not working quite as blind.

I'd be tempted to do the same as long as the "Cups" seem OK. I patched some interior areas similar to yours with fiberglass. Ours were really rotted out in the caged nut area.

Kaber

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My thoughts exactly. Nothing is really rotted out, just a few patches that I want to arrest any further corrosion and the cups, from the underside and what I can poke around from above with my finger, seem pretty solid.

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Hi David.

Be careful moving forward and try to poke around as much as possible before patching those holes. The trunk mounts seem to be another Achilles Heal of rust for the early Rivi's. In working on mine, I've found there are two issues with this area:

1. Water penetrates the trunk (either by bad window/ trunk seals or rotted window channel in which water penetrates the body sealer in the seam of the trunk floor/ inner fender.

or (and more probably)

2. The trunk body mount "cups" retain water as they are closed (no vent holes) and rot from the inside out. What looks like trunk rust is actually rot coming up from the cup and consuming the trunk floor.

The latter is what happens in most cases so the bad part is that which you usually can't see. While I had some rust in those areas, once I started to cut out the metal, the real challenge appeared. Not only was the floor rotted but the body mount cups (in the case of the drivers side) was nearly non-existent (passenger side had rot but was repairable without having to remove it from the car). Check out what was left of one of the body mount bolts once I peeled the floor back a bit:

post-71637-143142800444_thumb.jpg

Needless to say, I had some major surgery to perform in which one side required having to re-build the body mount cup and both sides of the trunk had to be repaired (along with repairs to the inner fender): http://forums.aaca.org/f177/trunk-pan-progress-looking-solid-rust-275117.html

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I suggest you get under the trunk and jab the cups with a flat-head screwdriver to see if what looks solid...........is solid.

Personally, I'm not a fan of fiberglass repair and metal is always better. Even if you made a patch panel and laid it over the top secured in place with JB Weld, rivit's or nuts/ bolts (Kaber, nice job on your repair, by the way. I must have missed that thread last year).

Long story short, just be sure there is not a bigger problem lurking underneath.

Mark

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Working fiberglass around rust is a band-aid from my meager experience. Eventually it will come back, and usually with a vengeance. Here was my thinking when dealing with the trunk area and the bracing: First, i have a mig/tig welder and plenty of replacement sheet metal that i can form. For flat pieces this is definitely what i lean towards. Welding and rust don't go together, If you try to weld a piece that is too thin or rusty it will disappear and run away from you as you are welding, so you are not left with a choice really. You either eliminate the rust before you weld or as you weld. Speaking from recent experience it is easier to deal with it prior instead of stopping your welding, setting things up for cutting/grinding, and then going back again.

Ok, so i removed all the visible rust from the trunk, leaving a couple of gaping holes above both braces. One brace had been rusted through. I cut the rust out of it and fabbed a piece to weld in. After removing the body mount bolt and getting things almost as good as new i hit everything i wasn't going to weld to with black rust converter. I'm not sure if it was necessary, but if it saves me work down the road i'll call it good. I then mig welded my patch panel and covered it with rust converter yet again after cleaning. i will be going over the floor from toeboard to taillight with por-15 silver, then seam sealing and laying down splatter paint over that.

So to shorten it, i cut out what i can and replace it. I use rust converter anywhere i welded and on anything i think might have a possibility of rusting again. Without a mig welder i think you could do the same thing with panel adhesive, rivets, or even fiberglass. Fiberglass would probably be my last choice.

Edited by devildog93 (see edit history)
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I agree with everything that DD93 says. If you're working to just cover a hole, and you've got the rust cut out and the exposed metal protected, then a fiberglass patch could work. But when you're dealing with a body brace, a mount, and bolts to hold everything together, you want to go back to the factory's reason for using metal. Not because it's easy to shape; it's supporting the weight of the car body and its inhabitants (you) for safety. I don't know that I'd even trust rivets or screws to hold that body to the frame as the frame gets flexed. Just my $.02. Just wait until some grease monkey wants to lift your car at the pinch welds and you have the frame hanging from the body mount bolts. Is the fiberglass going to hold the weight of the suspension, chassis, and engine? You're dealing with more than aesthetics here!

Ed

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Good points Ed. Nothing replaces a welding machine, but some of the new panel adhesives look like they would certainly work if you didn't have access to one. The problem with rust is there is always more that you can't see, so i try to attack it vigorously when i can. Playing catchup with rust is not something i want to do over and over. When and if i have to do it i make as sure as i can that it won't be coming back soon in the same spot. If you have access to a brace that is the time to hit it with converter and make sure the structural integrity is good rather than having a body mount break at an inopportune time, like while driving down the road. These cars are 50 years old, so fighting cancer is going to be a big survival skill for any owner.

Even if you don't have access to a mig welder, i bet you can find a muffler shop with an old hand welder that could help you out. I know i would patch a brace or a run a trunk patch in a couple of hours for just about anyone for a cheeseburger or two.

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Not nearly as bad as some I've seen. Those panels would be an easy repair for a skilled body man. Sometimes it's easier to break down and pay a professional to do this kind of work if you have no experience with it. It's not something you want to keep thinking about in the back of your mind as your driving down the road.

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The bad side i would cut out and replace. The brace looks good. Sand/grind off or derust it however you can and hit it with rust converter and call it done. The panel with the small rust holes - i would sand down to metal to see what i had to work with first off, but doesn't look too bad. Rust converter again, maybe some 2 part epoxy filler to fill holes then sand it down and put splatter paint on top of it after priming. All in all it is in far better shape than mine were. My good side was your bad side. I would be quick to cut out those panels if i saw rust though since you know there are braces underneath that will tend to collect water. Again, it isn't just what you can see. You have to assume both braces have had water in them a while. Probably nothing major, but you might want to get to them to hit it with something before it becomes more than a cosmetic nuisance. More for peace of mind knowing they will be a solid for a while if you attack them now while you are on it.

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