Talk Me Off A Ledge.... Bondo/body Filler

So I made the mistake of poking at a couple rust bubbles and uncovered a bunch of bondo that was failing under the paint job. Under the bodno was a haphazard weld job on the fender tops and some rust on the body panels near the rockers.

I've never dealt with bondo So My first instinct was to grind it down until I hit metal, spray some "metal ready" by por-15 to kill the rust (which requires keeping wet for 30 mins), and recover it with bondo.

I didnt grind of ALL the old bondo though cause I wasn't sure where the edges were. Just around where the rust was bubbling through.

After doing this, I finally read that bondo is poros and the old stuff might have absorbed some of the water I had rinsed it with before recoating.



Does anyone have experience with bondo absorbing water?

I'd love to just be able to sand it down and paint but I'm paranoid now that the wash I gave it before I filled the hole with new bondo might be permeated with water under there.

After my initial bondo recoat:

 

My instincts are telling me to regrind it all off, all of it. And then use something like "metal ready" or "metal to metal" instead of bondo.

Just wanted to get others opinion is to if i'm being too worried ad would be fine just sanding and painting as is.

Thanks in advance y'all. My ignorance to this process is what is causing my stress.

 

Yes, polyester body filler is porous.

Best method is to grind it all out (because other areas have rust growing), perform body work, prime with either self-etching primer or epoxy primer an THEN cover with body filler.

 

Bondo or polyester filler will absorb water. I agree with the above, grind it out, do your metal work, prime with epoxy or self-etch, then cover with body filler.

 

Maybe seal the area under the polyester filler with short strand fiberglass filler, then polyester filler.

 

I would pick a spot at a time. Grind it down to good metal. Prep it well and prime with etching primer and coat with 2 part epoxy primer. You can apply a thin coat of filler over the epoxy primer within the cure time. Some 7 days to fully cure. After it has fully cured the filler won't stick.
I like that Jeep same year as mine, but don't make the same mistake as I did.
I tried to do it all at once. Got the body on the rotisserie welding in new floors.
I wish I did the work in stages and kept driving it.
I will finish it one day, but arthritis has sure slowed the progress.
Haven't tried the Metal to Metal filler, but a lot of guys like it.
The short strand fiberglass filler is not bad to use not water absorbent.
Removing old filler that has let lose is opening a can of worms so do a section at a time. Catching the filler at the right stage of curing can sure cut sanding time.
Too soon and it clogs the sand paper. Too hard and it takes forever to sand. You'll get a feel for the right time and can sand it faster and more easily.

Dave

 

I have been professionally advised to never epoxy over self-etching primer. Something about the acid in the self-etching primer rejects the epoxy. Supposedly only 2k urethane primer over self-etching primer.

 

Good point. Has been a while since I used etching primer.
I think the last 2 part Epoxy I used was metal ready. Sherwin Williams 2 part Epoxy that I used on the garage floor.
I always use the same brand system. Don't mix different manufacturers. I usually use Nason products a Dupont product since they are close by. I have used their 2K primers. Reading the instructions lets you know what to use and how. Seems a lot of primers no days don't need etching first. I think I may try Southern Poly Urethane Products.
https://www.southernpolyurethanes.com/

Dave

 

"Best method is to grind it all out (because other areas have rust growing), perform body work, prime with either self-etching primer or epoxy primer an THEN cover with body filler."

If you do it the way "Stakebed" says above the epoxy primer will seal the raw metal, and the filler will adhere better to the epoxy primer than it ever did to bare metal.

The most common mistake in applying body filler is to apply it directly to bare metal. I think this idea comes from the days before we had epoxy primers, or perhaps it comes from the days when folks were using lead for filler, which has to be applied to bare metal, and then using the same approach with the plastic fillers came out. When done that way rust will invariably form under the filler and it will crack and fall out.

Don't wash the freshly ground area with water. Blow it off with compressed air, and then rub it down with a tack cloth. Water is only used afterwards when wet sanding the sealed and primed area.

 

If you are set on a bondo fluff and buff type job,at least do the first coat with some fiberglass reinforced stuff, long strand is more rugged short or chopped is easier to work with.

 

Thank you guys! Looks like I'll be grinding it out and redoing it. Thx for the responses.

I went to the paint shop today and got a quart of paint and a quart of metal-2-metal so I won't be using Bondo anymore.
The metal-2-metal claims to be waterproof and rust resistant so I think it'll be the best way to ensure I don't have to do the job a 3rd time lol.

 

A warning. I've used Metal-2-Metal. Great stuff, more structural strength than standard filler. BUT, sanding it after a full cure is like sanding a rock. OMG is that stuff hard! So try to apply the minimum and rough sand before it cures for days.

 

Got to give the Metal to Metal another try. I found it hard to work with.
The hardner split and I had to get more and had a hard time sanding it down.
Never got the ratio just right. I do like using the short hair filler.

Dave

 

Devil's advocate...stop picking at scabs

 

I have one Jeep that is held together with Bondo.

 

I'm with jeepstar.......
Having done a patchwork and paint job on my jeep and later regretted it.....
Just seeing what you have posted so far, I guarantee that there's a fair amount of poor work and filler under that paint. If the PO buried those little spots..... what else is waiting to rear its head....
I made my jeep beautiful.... only to have the PO's filler work come back to haunt me later on. I wish I had pulled the tub, blasted it and done the job right the first time.
What are you trying to achieve? I doubt your newly mixed paint will match to your satisfaction when spot touched up......

 

Yeah. I'd be inclined to 'wait and see' if it develops as a real problem.

If it ain't broke, don't fix it.


But I've always felt that body and paint were inevitably a losing proposition. I rather paint with a house brush and drive my jeep without worrying.

 

This is an interesting conversation.
On one hand, I wish I kept driving the 64. Taking the tub off, seems it's stuck on the rotisserie. Wish I was still driving it. But, when I finish it, I know it will be right.
I don't think I'll do a frame off again, but I couldn't let that rust keep going either.
Some very good points. Depends on how much time you have to get it all done.

Dave

 

Drove it until the body falls off and then buy a replacement. Put more bandaids on it and keep driving it.

 

hahaha!

Fingers crossed!!! The paint guy I went to spent an hour and a half mixing and matching in order to get the closest humanly possible. I was really surprised he put in so much time. It's not often you get that kind of service anymore. He's been there for 40 years so hopefully his expertise set me up for success. Time will tell I guess once I actually have a chance to paint.

Im trying to achieve a Jeep that is nice enough to take to car shows and maybe win some awards. I dont like rust and this seems to be the ONLY place on the jeep showing any questionable spots. I have a goal and I'm getting closer every day to achieving it. Learning as I go.

I'm not interested in having a beater. I've done that in the past. I've always wanted a show quality cj5. TO EACH HIS OWN

The jeep was frame-off restored 11 years ago so I think if there were any bubbles they'd already be showing... which they have been (knock on wood). I'm currently giving it a refresher restoration to get it back to it's former glory!

Since December I 've replaced the entire fuel system, cooling system, ignition system, brakes, updated the interior, etc..... I was hoping to not have to poke at the paint since at first glance it was nice. but my OCD took over for a minute.

Everything happens for a reason., I wouldn't have been happy unless it was perfect. Now I have a chance at getting it closer to perfection.