hey guys i was changing my wheels back from my snow tires the other day and i noticed that the entire underside of the main body was rusted out on my car!! it has not spread to the chassis but all the way down the inside of the wheel well and a little under the car and its spreading fast. what can i do? i was thinking about just taking a metal saw and cutting out everywere it is rusted and build myself a new structure in there. would this work?
rust fix under car
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Yea, that's bad. The other side maybe getting bad also.
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Cut back the rusted sections, much of it will break off with a little pressure.
Sand to bare metal and spray with phosphoric acid. let it dry, then wash, rinse, prime and paint.
Use scrap metal to mock up replacement and pop rivets to secure it. Paint patch to suit.
Easier than it sounds actually.
If you have or know someone with a welder, you can weld it on, in which case you can skip the prime and paint of the metal under the patch.
There are a lot of sites that detail how to make patches on car bodies, with different goals. some are strictly for looks, other stress function, others are for good looks and solid repairs.
The most difficult part with that repair will be access.
If you just want to stop the rust, cut off the horizontal parts, wash it out real good and spray with phosphoric acid, it's normally sold in auto stores as 'rust converter' , but can often get it cheaper from pool and garden supply shops. Then when the acid has dried, paint the interior.
It will keep mud and dirt from caking up in there and slow the rust.
Sand to bare metal and spray with phosphoric acid. let it dry, then wash, rinse, prime and paint.
Use scrap metal to mock up replacement and pop rivets to secure it. Paint patch to suit.
Easier than it sounds actually.
If you have or know someone with a welder, you can weld it on, in which case you can skip the prime and paint of the metal under the patch.
There are a lot of sites that detail how to make patches on car bodies, with different goals. some are strictly for looks, other stress function, others are for good looks and solid repairs.
The most difficult part with that repair will be access.
If you just want to stop the rust, cut off the horizontal parts, wash it out real good and spray with phosphoric acid, it's normally sold in auto stores as 'rust converter' , but can often get it cheaper from pool and garden supply shops. Then when the acid has dried, paint the interior.
It will keep mud and dirt from caking up in there and slow the rust.
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If you have panels welded in have it done with a 70 amp wire fed flux core welder min 120 amp flux core max. I have a 50/70, if your in h Va Beach area come on by, bring a old washing machine body and I'll weld new parts in cheaper than a body shop, granted I'm not as pretty as a body shop, but I guarantee if you bring a washing machine body it'll hold a long time. Used that in floor boards in an old Chevy pickup 25 years ago I sold the truck 5 years ago with solid floor panels STILL installed 
Well that part of the car is located under another piece of plastic that is the side skirt my main concern is the spread of rust would it be ok if I just cut that section of the body out were the rust is? It's not a major part and doesn't hold anything in place I think
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Yea you can cut it out, BUT what will happen if you do? That is what you have to consider when modifying a car body under side, will exhaust get in, water, cold air, hot air. Believe it or not there is a alternative to new sheet metal if its not a structural component, .......................fiberglass, easily obtainable at Wal Mart of the local hardware store. Just remember to use the cloth, not the mesh stuff.
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Here's one video, I didn't watch it so........you know
How to use Bondo Fiberglass Mat and Resin for body repair | Video « Wonder How To
but remember one thing with fiberglass wear a respirator and use gloves, you DO NOT want ANY of that stuff on you or in your lungs, and a sander will become your best friend in a hurry.
How to use Bondo Fiberglass Mat and Resin for body repair | Video « Wonder How To
but remember one thing with fiberglass wear a respirator and use gloves, you DO NOT want ANY of that stuff on you or in your lungs, and a sander will become your best friend in a hurry.
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And, NOT a palm sander!! Belt sanders are too brutal!! I have not used my palm sander since the purchaes of a random orbit sander.....that was many years ago. Now that we talking about a dusty process.........air compressor will come in handy. Gotta keep the dust blown out of the sander motor and bearings or it won't last very long. Blow the velcro pad, that the paper sticks to, off before attaching a new piece of sandpaper.....pad will last longer and paper sticks better. A cheap oil type compressor will do the job.....I gave up on the oil-less compressors years ago. Last one I bought was a Craftsman 3gal for $95.....might do better at Harbor Freight.....:4-dontkno An air compressor always comes in handy around the house.....seems that most times I go to the local gas station someone is putting air in their tires....after paying $1 to use the "air pump".....gee....:upset:. Most compressors come with a cheap flex hose and attachments.
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My personal favorite is a 4 1/2" disk grinder with a sanding disk on it I us the alu blending disks from Northern. But as SABL said do NOT use a palm sander or it will be dead real fast and a air compressor is a must. But if you us ea air compressor, spend the extra money and get a really good one that will power a pneumatic sander and go that route, its what we used on rotor blades in the Navy and we never had any problems out of the tools. AND if you mess up and make a indent when the glass is still wet, bondo sticks to fiberglass a lot longer than it does to steel. trust em I worked on Helicopters
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if its part of the unibody structure then fiberglass is out of the question and steel MUST be used
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