Rust advice

My civic has some rust at the base of the rear left wheelarch. I've posted a photo:
http://homepages.nildram.co.uk/~jainsw/civicrust.jpg
The panel seems to be at least partly hollow which explains the hole to
the left side. I've peered inside and I think it's a fibreglass structure - am I correct?
My plan is to sand down the area further and use body filler to seal. I'll then sand the dried filler and spray accordingly. Does that sound sensible?
Just in case some water has entered the cavity, will it drain out elsewhere? The plastic trim is plugged into that section of bodywork and there weren't any signs of water when I took out the plugs.
Thanks! Jez
P.S. there is no rust behind, only where visible on the outer-facing surface.
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Extremely common. Also check the other end of the wheelarch where it meets the rear bumper. If you don't have rust there now, you'll have it soon.

Not unless somebody has already tried to fix it. And it seems to me someone already has...
Have you got the car's old MoT sheets?

Nope. That rust is coming from the INSIDE, on account of condensation. It's too late now unless you do lots of cutting and letting in new metal. You can do whatever you like to the outside, and it will bubble back up again in a year or so.
If you really feel strongly about it, sell the car, buy a brand-new one, then apply cavity wax immediately you take possession.

It drains, but since it's enclosed and has trouble evaporating quickly, it sticks around long enough to eat through the dip primer and cause rusting.
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TeGGeR

The Unofficial Honda/Acura FAQ
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TeGGeR wrote:

All other areas seem to be fine at the moment but I'll keep a keen eye on them.

Both panels (on both sides) sound hollow. There isn't any damage on the right side but when I tap it, it really does sound like fibreglass ?

Do you think this will cause trouble in the future? It doesn't seem to be affecting important sections (e.g. chassis). I can contact the previous owner who will know if any work has been done.

have any cavities unless somebody has tried to repair the panel? How would a new car need cavity wax?

this car for a good few years - I'm a student at the moment and haven't got money to spend on a new car.
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They go from the inside out, so by the time you see it, it's too late.
Remeber the exterior panels have paint to protect the, but the insides of those same panels have primer only.

It should not be. Honda uses only steel there, and the area is quite hollow as it consists of sheet steel panels spot-welded together. There ought to be no foam, fiberglass, or crumpled newspaper in there. Your photo looks very much like someone has at one time made a valiant effort to get past the MoT.

You will only fail if the MoT inspector reckons the jagged rust is a hazard to pedestrians (true!), ...OR... if the rust is deemed to be within 30cm (12") of a structural area. Since the sills are considered structural, that hole is potentially within the fail zone.
Come MoT time, you may have no choice but to have it welded up, umless you can bodge it convincingly enough that the MoT man does not spot it.

That's iffy. You need to make sure the MoT man decides that that area is not "structural", and if he thinks it's structural, then he needs to miss spotting your filler repair. And I can't say from where I am...

You know how when it rains the paint gets wet? Well a similar thing is happening to the INSIDE of the metal as well. It also gets wet. But because the interior is enclosed, it takes a long time to dry out, meaning the water (and winter salt) has an extended time to munch through the primer and start the steel rusting.
The only way of preventing this is to keep the water away from the steel, and that's done in the UK with cavity wax, like Finnegan's Waxoyl, or Dinitrol. If you can keep the water from touching the inside faces of the steel, you'll prevent most of your internal rust, which is the kind that's fatal to the car.

I know exactly where you're coming from. Wish I could help more.
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TeGGeR

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I tried a similar repair on my '94 Integra. Six months later the rust was back, so I had a pro do it over. Been fine now for several years.
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Bob Burns
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Yeah, mine was rusting around all 4 wheel wells. I sanded it it under there was nothing left but a hole, filled it in with some sort of putty and fiberglass, painted it with rust paint on the outside, and but some rubber underbody spray on the inside, it stayed good for the next couple years, then I sold it, so who knows it might have started rusting again right away for the new owner :)

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Jez wrote:

I'd paint the rusty areas with POR-15 (a paint converter/stopper) first. If you can, replace the panel with a replacement panel. If the rust is under the paint, get it down to bare metal first.
Remco
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Yes. Pep Boys (an American discount auto parts store), for one, has a section dedicated to body repair plastics etc. I suggest perusing this area. If you're in the UK, I expect similar auto parts stores would have similar sections.
I had a more extensive problem in the same area on my 1991 Civic LX, but with both rear wheel arches.
I cleaned the areas as best I could, then applied a few layers of x, y, z body filler (can't remember which one I used) from Pep Boys over a few weeks. I used some netted backing tape (ordinarily for house wall plaster repair jobs) among the layers to promote support. All was let dry, then sanded a little, rinsed, let dry, then spray painted with a can of "Color Place RustControl Spray Enamel" from Wal-Mart. It's a high gloss paint that had a close match to my car's color. (Masking taped the parts I didn't want the high gloss on). Looks much _much_ better. It's held up over a year now. It's firm to the touch and shows no evidence of deterioration.
The amount you have to repair looks easy in comparison.

Not sure. I do know the rust has not returned on my 91 Civic. On the other hand, my 91 Civic was driven in the snowy northern U.S. for something like 2/3rds of its life. It now resides in the much drier (but still sometimes rainy or snowy) Western U.S.
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You have gotten some good advice from other posters but allow me to add one thing. A large part of the problem arises from the collection of dirt in the hollow area and the "U" shaped rim around the wheel opening. That channel fills with dirt and when it gets wet it holds the moisture for a long time causing the area to rust badly.. Before you do any spraying, painting, etc., clean all of the dirt, mud, and debris out of that channel and from the inside of the fender. ...
Dave Dodson
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I'm having the same problem. Can you send me the answer when you figure it out?
Tom snipped-for-privacy@postmasternetworks.com

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