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Removing large quantities of Bondo

8K views 44 replies 12 participants last post by  BRShirk 
#1 ·
We're talking Bondo of 3/8"+

I've thought about trying to tap with a deablow hammer to try and loosen the stuff and pry with a scraper. I'm a rookie.

The pic isn't good but the line on top is about where the metal is...
 

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#3 ·
You could grind it out with 24grit. Makes a lot of dust though. Depending on the location and thickness of the metal, I've had great success using a torch to heat it from the backside, then just scrape it off with a puttyknife.
"But it will cause trouble with the metal!" you say. Well, if the mud is that thick, you've already got trouble with the metal. A little heat won't hurt.
 
#8 ·
One of the top tools in my inventory is an industrial soda blaster. The thing requires me to rent a diesel pull behind air compressor to run it. But I had a 69 cj-5 where both fenders were screwed down to the tub bondo'd under and over the (roof flashing) then bondo'd over that and it was over 1/2 an inch in places.

The soda blaster tore though the bondo removing mil upon mil without causing any more damage.


There are low cost/capacity ones out through eastwood or harbor freight that work good they just take a bit longer to get the job done.
The end of the day though your only removing the junk leaving the good stuff to patch with using a soda blaster. Using a grinder or even wire wheel your going to tear into stuff you do not want or your going to be there all day covered in dust. Break out a soda blaster and shoot the area standing there and then wash the car off and bam your done.

Almost every part of that car can be hit with a soda blaster(the interior not so much). You will find it is a great tool to have in the shop. If you have encountered this type of spot there is no doubt other questionable repairs.

The thing will pay for itself in cleaning areas like the front suspension where you can shoot right over the rubber removing layers of grease and muck before tearing down the suspension. Have rusted rotors? That's a quick and easy fix.
Here is a fun one. Have body mounts bolts(or any other bolt) that are covered in a caked layer of rust on the threads? Before you break out the torch and fry your rubber bushings. Hit the bolts with a soda blaster and watch the threads revel them selfs enough for you to remove the bolts saving the bushings and not heating up the floor.




The tool is one of those things you will find you have reason upon reason to use it once you have it. If you have a air compressor up to the task then spending hours with a wire wheel, sanding, or grinding will seem not as good. I have been there and would not go back unless I was being paid to do so.


Heck I just did 2 truck racks for my boss on Monday and Tuesday for the new trucks they have coming in. It took me and another person 4 hours with a wire wheel to prep each one down to bare metal with many uneven surfaces and layers of paint. The whole time I am thinking If I just had the blaster it would have been an hour each (just me) tops to prep them down to metal. But, I am getting paid to do it there way. :rolleyes:

The soda blaster pays dividends once you start finding all the things you can use it on. On a project like yours your going to find that it will come in handy in many situations saving you a great deal of time and pain.
 
#10 ·
Every once in a while I get one stuffed with bondo, I usually get a three point painters putty knife and a hammer and chisel it off, you wont find anything faster and cleaner you'll be popping off 12"x12" chunks very quickly. Any panel like that needs replacing, all you really want to do is see how much needs replacing.
 
#11 ·
propane torch and a brush. a simple pass across the surface will pull the solvent out and turn it to dust. do not heat it just pass the flame across it.

we all know about soda so i'll leave that alone.
 
#14 ·
I see on soda.

I just wasn't looking forward to endless sanding on the worst spots. Once most of the mud is gone would you recommend sand blasting after I have the body braced? Or should I same that for after the major repairs are done as a run up to paint?
 
#15 ·
Sooo, we have round 1 of rust removal. The good thing is there's metal under there and it's pretty decent. This took about 2hrs. The one pic is a 3/8 drive extension for scale.

I started using the torch and wirewheel technique but ended up getting the mud hot and used a chisel to scrape huge chunks off.
 

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#20 ·
That's some nasty craftsmanship, I have seen worse but not many. I hope you picked the worst panel to start with. Forget about getting any more of the bondo off, Its as I said, only much worse. The skin needs replacing, mabee even the inner structure (replace door) you should remove the door and give it a good inspection from the backside. Give the jamb a good looky over too, in case its been hit.
Under no circumstances should you continue on with that skin, get rid of it. Even if you made your own skin and it was your first time it would come out better than that, because you wouldn't be using rivets and anyone that's asked how to weld on this site has done better welds while practicing on their first attempt. I don't know what part your looking at when you say "its not that bad" but I'm saving this picture and enlarging it so I can hang it on my "wall of shame" it really does suckass.
 
#23 ·
I thought it was a 4dr, that shadow threw me off. Now that you mention it I can see its a 1/4 panel. Unfortunately that makes things much worse. What you should do is go to the same spot on the other side and see if its the same. You want to find out if its been spliced together. If its a 4dr turned into a 2dr as Brian suggested its not safe to drive and will take extensive structural work before you can do anything with the 1/4s. also check the floor and frame, it shouldn't be hard to find if out it has been spliced.
 
#24 ·
Not to repost what's in my build thread, but the frame looks like the body so I'm using an S10 frame. The fenders, cowl, doors and jams look OK to my untrained eye. I've been looking on YouTube and have a book on fab on the way.

I think the car is salvageable but it'll be a total custom. By going that route I can fix the mess this patch panels, sheet metal, 1x1 tubing and buckets of sweat equity.

I'll repost the concept pix and build thread link. There's some pix there that show the insides.
 
#26 ·
Let me restate on the fenders. There's a pile of Bondo on them but from feeling the underside it appears the mud isn't covering pop rivets. Behind the wheel wells are bent in and I think with some heat can be straightened.

I'm thinking of stretching the body about 7" behind the doors and stopping the passenger area there. Then making a small pickup bed. To make the new back half and floor sound I'm planning to build a 1x1 square tube cage structure.

It's definitely a project. It'll be unique when it's done.
 
#27 ·
Deadbodyman, I'd love to see your worst pic.

By not bad meant the metal itself. With what I have planned I can work with the mess on the back half. I've found patch panels to help me make the body sound. My nephew went to school for welding but went into machining. He's going to help with structural welding and criticize my amateur attempts. But hey what's family for...
 
#29 ·
Well I did some more poking around and it looks like the previous owner spread the body to fit the seat. It looks like they just threw aluminum on the floor but left the roll pans intact. Well now I can use the sheet aluminum for interior panels.

I'll post some pix once I get to the point of pulling floor up.

I think the best way to make the body sound, since it's missing the integrity of the roof, is to make a metal skeleton to hang the sheet metal off of. I'll be able to correct the body lines and I won't have to worry about taking my kids for a ride when it's done. Opinions?

As wierd as this is turning out to be I'm really wanting to put as wierd an engine in it. Current leader is an OM617 Mercedes 5cyl turbo diesel from the early 80s.
 
#31 ·
I'm not sure why everyone is so quick to condemn this thing... I mean sure it's easier to start with pristine sheet metal but we don't always have it, and depending on the tools at your disposal it might be easier to fix it.

One of my current projects had about 1-1/4" of bondo on one quarter and about 3/4" of bondo on the other (FWIW, heat, knock it off in chunks and then clean the rest up with a cup brush on an angle grinder... Less than an hour's worth of work), on a car that would be much easier to get new quarters for (I actually have a parts car with OK quarters on it sitting in front of it) and i decided to fix them. The worst part was that the side that had 1-1/4 was riddled with holes from someone trying to use an old school, screw in dent puller.

In that case I spent the first day removing interior panels to get access to the back of it, knocking the bondo off, hammering all the screw holes flat, filling them with a MIG (back that up with some copper wrapped around a body dolly so I didn't have much if any weld sticking up in the back of the panel) and grinding the welds flush. When I got the chance I would cool the welds with a wet rag to start shrinking the panel also.

Day 2 (these aren't full days in a shop, this is messing with it in the garage/driveway) was mostly hammering and using a shrinking disk, sometimes using a propane torch to heat things up.

After day 2 I had it mostly the right shape and in the right location, day 3 I had to move on to another project and just spray bombed it to keep it from rusting sitting outside, no filler on it. It's close enough that with semi-gloss black paint on it most people don't even notice it, there's just a few light ripples in it and spots where you can see ground down welds that could easily be covered up with less than 1/16" of filler.

It would have taken me MUCH longer to cut and fit 2 quarters, and I couldn't tie up garage space that long (as it is I ended up having to heat the quarters with a propane torch on a november 40* drizzly day in the driveway to spray paint it).

The dent on the 3/4" thick side also went completely across the door that I'm not going to bother fixing, I have a second in the basement that will just get swapped, but that's way less work then hanging quarters
 
#32 ·
Some peoples kids shouldn't be allowed to play with tools and cars. Not mine though, my cheif helper and son found the metal on the door and door structure.

After round 2 of Bondo removal it appears my car WAS a Fordor hump back. A cool style itself, but that's gone so let's move on.

I found some things I expected and some not so much. The random bits welded, badly, for no apparent reason were unexpected. The decent lines on the doors, around the fender and what's left of the roof also unexpected. So it appears that with my plan to do a custom the main parts are good to go.

But on a good note, I found a parts source locally. The gentlemans father had over 100 cars in various stages. Evidently 35-36 Fords were his thing. He has a 36 coupe in near pristine original condition and a Model T in the same shape.
 

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#34 ·
Some peoples kids shouldn't be allowed to play with tools and cars. Not mine though, my cheif helper and son found the metal on the door and door structure.

After round 2 of Bondo removal it appears my car WAS a Fordor hump back. A cool style itself, but that's gone so let's move on.

I found some things I expected and some not so much. The random bits welded, badly, for no apparent reason were unexpected. .
I was just looking at your pics and had a great idea when I read the words kids and cars. Its a new game called "Toss a Patch" You get a substructure and a bunch of magnets and toss the patches at it from a few feet away (like darts) Hmmmm I might be on to something here. but it looks like someone already thought of it.:drunk:
 
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