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When Is It Shameful To Use Bondo?

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Old 10-21-2009, 02:38 PM
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When Is It Shameful To Use Bondo?

Guys, I'm restoring my car on a budget here. While I'd like to stray away from any and all bondo work, I don't know how to weld, and I think riveting in metal would be a poor choice for my application, so here goes.


The outer window sweep on my driver's side door failed some years before I owned the car. This allowed generous amounts of water into the door that the drainage holes apparently couldn't cope with. I replaced the window sweep with a brand new re-production window sweep. The piece fits and seals nice, but unfortunately the damage to the bottom of the door had already been done. There was significant rot along the underside ledge of the drivers door. Only the underside though. No rot had managed to make It's way up either side of the door. The only way you'd know it was there was if you layed on the ground and looked up at it. I also noticed something very strange; the entire inside of my passenger door has been undercoated but the driver's door is bare metal

I scrubbed the rot with a wire brush, prepped it and heavily coated it with POR-15 silver. The POR-15 did an excellent job of sealing the rust, and now both the bottom underside of the door and the bottom inside are forever encased in the stuff. The POR-15 Also did a good job of filling and sealing all the small pinholes and swiss cheese areas, but there are still two holes it didn't manage to fill. One is about the size of a dime, and the other is a rectangular shaped holes the size of your pinky finger. I was wondering what everyone's take on using bondo on these areas is. My idea was to lightly sand the POR-15 to rough up the surface, then apply a thin layer to add a smooth even texture to the door and fill the holes. Once the car is repainted, you'll never know it was there. Since this is a non load bearing area and the rust has been neutralized from further spread, I personally don't see much of a problem with this approach. I just wanted to see what everyone else with experience in the area thought. Thanks.
Old 10-21-2009, 02:53 PM
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Re: When Is It Shameful To Use Bondo?

"Bondo" or body filler should not be use to cover up holes ever. but there is stuff called tiger hair that some people use to fill holes. I don't really think that this is the way you want to do this repair on a car you are restoring. IMO you should find some one to repair it right. and never have to redo it again. The touble with using "bondo" or tiger hair is that after a couple years it will begin to crack, esspecially if water get behind it. If you went and spent the money on POR-15 you should just spend a little more money to get it repaired properly.
Old 10-21-2009, 03:12 PM
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Re: When Is It Shameful To Use Bondo?

It's only shameful to use Bondo in a way it was never designed for. Bondo is a very useful tool in body work. The problem is a lot of people have used it in a manor in which it can't and won't ever hold up. Unfortunately, you are describing such a use. Your post already identifies that you know that welding a patch would be the best solution. Being a do it yourself-er like many of us and even though you lack one skill, you are hell bent on using another for a solution. Good for you!

With that said, her is my suggestion. If you can't weld and are looking for something to fill those holes. Use something that can hold up better to moisture. I would use fiber glass. (Gorilla Hair, Tiger Hair, etc.) No matter how good your window seals are, you will still get moisture in the door. Bondo will not handle any moisture at all. Moisture will bubble it up and it will fall off. Fiber glass will withstand this situation much better. I would still make sure that you seal both sides of the repair very well and make sure that any excess water has some place to drain out. Hope this helps and good luck!
Old 10-21-2009, 03:14 PM
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Re: When Is It Shameful To Use Bondo?

Originally Posted by Iroc-Z28Man
"Bondo" or body filler should not be use to cover up holes ever. but there is stuff called tiger hair that some people use to fill holes. I don't really think that this is the way you want to do this repair on a car you are restoring. IMO you should find some one to repair it right. and never have to redo it again. The touble with using "bondo" or tiger hair is that after a couple years it will begin to crack, esspecially if water get behind it. If you went and spent the money on POR-15 you should just spend a little more money to get it repaired properly.

To me, this doesn't make a whole lot of sense. Yes, I went ahead and spent the money on the POR-15, because the kit was only $35. Now when you say to, "get it repaired properly" I assume you are talking about having a shop cut out the rot and WELD new metal in, thus not only defeating the purpose of a cheap repair but also doing away with the POR-15 work I just did and throwing that $35 right in the toilet. For such a miniscule area, wouldn't another POR-15 product work just fine? They make a body filler called straightline, but they also make a product called POR PUTTY I was thinking of using to fill in these small areas. As for the bondo, can't it be used on just the surface of the area that has the POR-15 to give it a smooth texture?




Here is the POR PUTTY:

http://www.por15.com/EPOXY-PUTTY/productinfo/PU/

It's so strong you can drill and tap it, yet gentle enough that you can apply it with your bare fingers.

And since it's WATER BASED, you can simply wet your fingers, and work with it until it is almost perfectly smooth before it dries - eliminating most sanding! But when it cures, it's ROCK HARD, making it perfect for repairing steel, plastics, concrete, etc. Amazingly, it even sticks to damp surfaces, and will cure UNDERWATER, so it can be used to fix leaking basement walls, swimming pools, plumbing fixtures and so much more.
This makes me believe that POR PUTTY will make a good filler for these areas.



EDIT: Just read your post craftman. I guess it wouldn't be a good idea to use Bondo even for smoothing out the surface. But would be a good solution then? Possibly some fiberglass, if you can sand it? I've never worked with fiberglass before.

Last edited by FireDemonSiC; 10-21-2009 at 03:19 PM.
Old 10-21-2009, 03:21 PM
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Re: When Is It Shameful To Use Bondo?

If you're going to repaint the car then why didn't you just get another door? They can usually be had for under $50 each. Then you wouldn't have had to worry about patching up rust holes.
Old 10-21-2009, 03:27 PM
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Re: When Is It Shameful To Use Bondo?

Fiber glass can be sanded just like Bondo, it just isn't as smooth when done. You could even fill the holes with fiber glass and then finish with Bondo. You just don't want to leave any Bondo exposed to any moisture on the reverse side. The fiber glass filler also mixes in the same manor as Bondo and it's water proof.
Old 10-21-2009, 03:28 PM
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Re: When Is It Shameful To Use Bondo?

Originally Posted by FYRCHKN
If you're going to repaint the car then why didn't you just get another door? They can usually be had for under $50 each. Then you wouldn't have had to worry about patching up rust holes.
Not sure where you get your parts from, but out here I'd be afraid to to ask the price for an entire door from a yard that wanted $100 for an "as is" ECM and $800 for an engine with 112,000 miles.

For such a minor area, it seems kind of silly to replace the entire door when the original one can be fixed with a little gruntwork.
Old 10-21-2009, 03:50 PM
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Re: When Is It Shameful To Use Bondo?

Originally Posted by FireDemonSiC
Not sure where you get your parts from, but out here I'd be afraid to to ask the price for an entire door from a yard that wanted $100 for an "as is" ECM and $800 for an engine with 112,000 miles.

For such a minor area, it seems kind of silly to replace the entire door when the original one can be fixed with a little gruntwork.
Craigslist is your friend. I hardly ever buy body parts from the junkyard anymore. Around here if you don't speak spanish then they triple the price on you nowadays.(That is an actual fact.) I see doors on CL all the time. A member in my local club has 2 or 3 pairs sitting behind his garage that can't hardly even give away. They are the most plentiful parts for these cars.

I was simply asking the question since you said you don't know how to weld.
Old 10-21-2009, 04:07 PM
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Re: When Is It Shameful To Use Bondo?

Originally Posted by FYRCHKN
Craigslist is your friend. I hardly ever buy body parts from the junkyard anymore. Around here if you don't speak spanish then they triple the price on you nowadays.(That is an actual fact.) I see doors on CL all the time. A member in my local club has 2 or 3 pairs sitting behind his garage that can't hardly even give away. They are the most plentiful parts for these cars.

I was simply asking the question since you said you don't know how to weld.

I didn't take offense to the question, I just thought it was kind of a silly idea to replace the entire door, and ride around with a mismatched door until I can afford a paint job. The area in question is very small compared to the door as a whole, is easily fixable with the right technique and is out of plain sight. This weighed against the idea of replacing the whole door doesn't seem worth it.

Texas like an area that is plentiful with thirdgens. BUt out here in VA, especially in this area of VA, It's every man for himself :/
Old 10-21-2009, 08:48 PM
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Re: When Is It Shameful To Use Bondo?

my opinion,if yo have tin snips cut a patch slightly larger than the hole.buy some fiberglass with the area clean put fiberglass on the inside of the hole and place the patch on it while the fiberglass is still wet.it will basicly glue it to your door.when its dry 15min or so smooth the outside with fiberglass and sand it with 80 then 120 grit paper.some primer and paint it will be fine.hit the inside of the door with undercoating.im a welder fabricater i cut rust out and replace it right but back before i learned these skills i found that this works great and lasts a very long time.not everyone has the money to buy new panles etc.trust me you wont be disopointed..its a easy repair.....hope that helps
Old 10-21-2009, 09:12 PM
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Re: When Is It Shameful To Use Bondo?

FWIW I hear there is some panel adhesive that guys swear by- but I have not used it. ( got me a miller and use it allot!)

I remember some book about the third gens metal being glued in spots at the the last few years of production.

I would only use filler on an area that is backed up with the steel to help it from cracking. There are different types of filler too, harder with metal powder or glass strands to the softer pink or green kind that does absorb moisture but "edges" out nice when sanding.

I use different stuff depending on what I am trying to fill but almost always finish with a glazing putty- I like evercoats metal glaze that "cross links" with a catalyst hardner. HTH


Oh and I agree with chicken these doors are not hard to find and would be a good way to go.

Last edited by steve87ta; 10-21-2009 at 09:16 PM. Reason: forgot door
Old 10-21-2009, 09:17 PM
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Re: When Is It Shameful To Use Bondo?

Originally Posted by FireDemonSiC
I didn't take offense to the question, I just thought it was kind of a silly idea to replace the entire door, and ride around with a mismatched door until I can afford a paint job.
If your worried about your $35, why patch the hole only for it to fail after you can finally afford paint? Just wait to replace the door when you can afford paint.
Old 10-21-2009, 10:29 PM
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Re: When Is It Shameful To Use Bondo?

I'd like to make it very clear that I am NOT replacing the door.
Old 10-24-2009, 08:12 PM
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Re: When Is It Shameful To Use Bondo?

new to the forum but thought i would throw in my two cents, if you dont know how to weld but can clean up the holes, make your own patch you might be able to find a local muffler shop to weld it on for you. if you make your own patch make sure all the corners are round, at least 1/4 on the corners. if not he metal will tend to crack in the corners. do the same on the cut out.

if your using fiberglass a few tips are to get a fairly thick clear plastic and place your cloth down on this, pour an amount of resin onto the cloth that is approximately the same weight as the cloth ( 3 oz cloth/ 3 oz resin.) put another peice of plastic over the cloth and resin and use a plastic squegee like for bondo to spread the resin evenly. then you can cut the shape of the peice you need using the plastic to lessen the mess. peel one side place your patch and then peel the other side. this not only lessens the mess of working with the resin, but also helps you apply it in the smoothest fashion possible making sanding easier.

also remember depending on what type of resin you use beware of pot life. some resins set up really fast especially cheap resin from walmart, but that stuff you can mix a little light on part B and get some more pot life.
Old 11-21-2009, 12:05 PM
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Re: When Is It Shameful To Use Bondo?

I saw you mentioned POR PUTTY. that stuff works great. I would assume you bought a starter kit, with the marine clean and the zinc stuff?

should be a rather solid fix IMO if you followed the directions to a T and use the POR PUTTY...
Old 11-21-2009, 12:16 PM
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Re: When Is It Shameful To Use Bondo?

If its such a small area and you dont really want to spend a bunch I heard some people used JBweld for like plumbing on small holes like that that arent really visible. Its like a 2 part mix and its real solid once it dries. I don't know if thats the best solution but Id try that before bondo since its made for plumbing and can withstand water.
Old 11-21-2009, 05:15 PM
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Re: When Is It Shameful To Use Bondo?

ok so for starters YOU CAN NOT FIX RUST!!! it will always come back. best bet is to get an LKQ or economy doorshell and do a parts changeover. next best thing if you can not weld is to do this... cut out your rust and get some sheet metal and form it to the body-line of your door( but make the replacement patch bigger than the hole you cut out) then get some panle adhesive(glue) its a 2 part expoxy so your going to need an epoxy gun, AND GLUE THAT SOB IN FROM THE INSIDE SO ITS INSET! then squeeze it tight and wipe off the exess and let er' dry. then get some EPOXY PRIMER(next best thing from factory e-coat) and get a special aplicator spray gun with a long hose and spray the inside of your door( or just have a collision shop do that for you. and then SPRAY SOME EPOXY PRIMER ON THE OUTSIDE OF YOUR DOOR ON BARE METAL AND SCUFF IT UP BUT DONT BURN THROUGH TO BARE METAL. THEN YOUR GOOD TO ADD YOUR FIBERGLASS FILLER AND YOUR BODY FILLER AND THEN GLAZE IT IF YOU WANT TO. then just spray some primer surfacer over everything. then primer sealer then your base and clear coat. rember never apply any body filler over bare metal, and if you do have bare metal use epoxy primer!!! always.
Old 11-21-2009, 10:17 PM
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Re: When Is It Shameful To Use Bondo?

It's only shameful to use Bondo in a way it was never designed for. Bondo is a very useful tool in body work

very well said...
Old 11-23-2009, 09:04 AM
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Re: When Is It Shameful To Use Bondo?

I would not use the word "restore" with the options you are planning on using. If you can't fix the job the correct way or by replacing the part, then that kind of a repair is called a "hack job". You will be addressing the issue again down the road. Are you planning on a good paint job or a Maaco paint job? If your plans aren't to do a great finish, then what does it matter to drive with a mismatched door for awhile? The car doesn't sound like something that will "ooohhh" the masses as you driv by as it is.

Sorry if this sounds offensive, but I don't understand the purpose to fixing something if you can't fix it correctly.
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