Tips on using Bondo Please

[Suprastic]

Today I started to sand down a few rust spots on my car that were starting to bubble behind the paint about the size of a dime (rear 1/4 panel). Aftersanding down, then cutting away some of the metal (about 2" long and .75" high) to get all the rust out I used a wire brush, sand disk, and rust converter to remove all the pits and rust off the surface. When I was completley sure that all the rust was gone from both side of the panel I sprayed it with automotive rust primer (Tremclad) to reduce the chance of it coming back in the near future. The rear quarter had a rather thin sheet of metal then a hollow space and a much thicker/stronger metal behind it (im assuming it might be part of the frame.

My question here is, should I just Bondo the 1/4" gap between the outter 1/4 panel and the metal behind or should I use a metal mesh screen between the 2 panels and then bondo over the mesh?

All thoughts and opinions are appreciated.

Thanks,
-Dan

 

[Jeff Lange]

My thoughts: you should weld new metal in, grind it smooth, then bondo only to fill imperfections.

 

[T34418L3ONE]

i 2nd that, use bondo to smooth out panals, not fill in gaps. Rule of thumb, use as little as possible

 

[Suprastic]

I was thinking the same thing, but came across the problem of not having a welder and no neighbours or freinds have one either. Is there another alternative? What about a strong epoxy for metal surfaces, such as epoxy steel? I was doing more research and found out that fiberglass resin is better to use than bondo on areas larger than 1" and will not crack like bondo. Anyone?

 

[Justin727]

I wouldnt suggest bondo. I long strand hair fibre Glass filler.(dynalite)iirc.
be a little more specific. is it like a bridge of empty space ur lookin to fill or just build up? I would suggest welding/filling but be a tad bit more specific. if its just deep no big holes then sure use the filler. Then a finishing filler say like evercoat metal works. Take pictures maybe then i'll be better at helping you with your problem.

 

[mkIIIman089]

I know you want to do it yourself obviously. But might I reccomend just going to a body shop because they do have the experience and equipment to weld in a plate. Then you can bondo it yourself and finish it to your quality.

 

[HyRisk]

HUH?!?! You said the B word! Sound professional to just say body filler. Ahhh...yes. Body filler is a nice word. Anyways, if your dealing with the chassis use a mig welder. Or take it to a automotive repair shop and tell one of the guys to do a side job for ya real quick. Give em 20 bucks on a weekend and call it a day. Theyre ASE certified and know what their doing. Besides. You want to maintain the structural integrity of your vehicle. Thats my point of view on the matter. anyways.....if you wanna be cheap about it go with fiberglass. i wouldnt recommend it though

 

[Suprastic]

I know you want to do it yourself obviously. But might I reccomend just going to a body shop because they do have the experience and equipment to weld in a plate. Then you can bondo it yourself and finish it to your quality.

The car is in winter storage and I'd have to get it towed down to a body shop. Since the car doen't have any panels or interior on it, that isn't really an option for me. Thanks for the advice anyways. Trust me I would do it if I could.

 

[Suprastic]

HUH?!?! You said the B word! Sound professional to just say body filler. Ahhh...yes. Body filler is a nice word. Anyways, if your dealing with the chassis use a mig welder. Or take it to a automotive repair shop and tell one of the guys to do a side job for ya real quick. Give em 20 bucks on a weekend and call it a day. Theyre ASE certified and know what their doing. Besides. You want to maintain the structural integrity of your vehicle. Thats my point of view on the matter. anyways.....if you wanna be cheap about it go with fiberglass. i wouldnt recommend it though

I'd have to find someone that could come to my garage and do it for me, which could be hard. BTW, what are the disadvantages of using fiberglass?

 

[Suprastic]

I wouldnt suggest bondo. I long strand hair fibre Glass filler.(dynalite)iirc.
be a little more specific. is it like a bridge of empty space ur lookin to fill or just build up? I would suggest welding/filling but be a tad bit more specific. if its just deep no big holes then sure use the filler. Then a finishing filler say like evercoat metal works. Take pictures maybe then i'll be better at helping you with your problem.

The rust was on the pass. rear 1/4 just above the wheel well lip. when I scraped all the rust away it went though the outter body of the car. Behind that thin layer of metal is what I believ to be the metal wheel well housing or something. The gap between the two is only about 1/4-1/2" deep. The wheel well housing is solid metal and the rust didn't "eat" through that at all, so this provides a good backing for the filler. View Diagram below:

 

[tte]

Your best bet is to weld it...But if for whatever reasons you have that you cannot weld it you could use the wire mesh with epoxy resin. Just use a filler to thicken the resin after you have mixed it with the catalyst...Fillers like talc, microballoons, milled fibers, carbosil....

It best to use as little bond as you can.Would not recommend bondo to fill in big cracks or holes.

Or if you know how to weld correctly or have a friend who knows how to weld correctly just go buy a welder and weld it and then return the welder and get a refund...I heard of some people doing it and it works.


Cheers,
Roy

 

[Justin727]

If it isnt terribly deep filler wouldnt hurt it. If you have something to build up off of. scuff the metal w/ 36 grit or 80 grit so the filler will have something to grab a hold of. Use Long strand fibre glass filler first then cover and blend in with evercoat metal works or something similar. If you can get a picture of it I can help you more with this.

 

[oneandgone]

Guess what I do everyday....

Since you aren't up to welding in new metal do this....

Go to your local auto body supply store.

Get a tube of Duramix Small Metal Panel Adhesive and a gun to apply it with. Also, get a polyester 2-part body filler, 36, 80, and 150 grit sandpaper.

Cut a patch panel. It will need to overlap the good metal around the repair area.

Grind (or 36 grit) the mating surfaces of your patch and existing 1/4. The Duramix needs a rough surface to bite to, and is stronger than welding. Also, it will not leave an unreachable bare metal area on the backside like welding would.

Glue the panel to the car.

Sand off excess glue.

Use filler to smooth the repair area. Start sanding with 80 grit and finish with 150.

Prime, prep, paint.

 

[Suprastic]

I measured the depth of the area and it is only really 1/16" deep. I didn't measure it before, so i'm not sure if this difference in depth will make a big difference. Will be necessary to patch the gap or should I just fill it in. I'll post pics tonight sometime.

ONEANDGONE, that's exactly what I was refering to. Thanks, now I know the name of the stuff I have to buy if I absolutely shouldn't just fill it in. Also knowing that it works is great!:biglaugh:


-Dan

 

[tomjan87]

ok, just for your hassle, i would just go buy a welder, im sure youll use it again sometime. I use mine all the time. my 2 cents.

 

[Suprastic]

Ok, you guys talked me into it and I bought a welder and a roll of sheet metal. I'm welding the piece of sheet metal to the outside of the hole and NOT the inside, right? I have no access to weld it from behind because it is solid metal back there. After I grind it all down, won't the metal in the center of the patch be almost paper thin? Or does the body filler correct that.

 

[oneandgone]

You just want to grind the welds smooth, not the rest of the panel. You will need to sand it so that the filler will adhere though.

You won't be able to weld the backside. The welds you make on the outside will penetrate into the back though and leave a bare metal area that you will have no way of coating for corrosion protection.