bondo!

[jskeetz]

so my dad gave me his car.. he did some bondo work a few years back but he never primered it and now the bondo is hard not soft...wat should i do ...i wana prime it..

[stretch JDM]

re sand it man .( the bondo spot. ) not a big deal.

[jskeetz]

ohh yeah thats it wit some hard sandpaper

[SOHC-FTW]

Bondo will only stay soft until its harden which when mixed right is 5-10mins.After that its still soft enough to cheese grade to get it in close shape.But after 40mins+ its as hard as it will ever be.Since you seem to not know the hows and whys about simple filler than id take it to someone that does if i were in your shoes.Another thing is that spot has been in the elements of god knows what for years best to take it all off and redo it and pull the damage as much as possible without any high spots.To take it off you will need an air hand held grinder with a 36grit pad.You can always block it but that would take awhile to get down to bare metal.Eitherway that old un primed mess needs to come off and needs pulled and re worked.If you dont have the skill or know how then attempt at your own risk!TAKE it to a reputable shop.(Also they might still be some good bondo under there,but i wouldn't chance it if i was you.I've been doing bodywork for about 5yrs and ik a few things hope this helps.

[SOHC-FTW]

All this info depends on the size of the worked area aswell.

[Dobermann]

Bondo and primer will not seal out moisture. It is most likely water logged and useless. My guess is that its quarter panel rust, and that your dad bondo'd over the rust.

Buy a haynes manual on body work. They are usually available at the library as well.

Post pics!

[bryce.martin23]

I agree with most of these posts. Grind the filler off completely and re-do the job from scratch. Make sure to seal with a primer though right after to avoid any moisture to soak in. As a note also, primer is very porous and will also absorb moisture if given enough time exposed to the elements. General rule with body work is to finish all the way through, its not recomended to roll around in primer for months. Waste of time and money.

[kstella91]

If i were you i would redo it. after the new bondo is set up use a DA sander with 220grit until you get it to shape..then i always do 3 or 4 coats of primer, only because sometimes you will get tiny holes in the bondo and primer will help fill them. then sand it with 320grit then wipe it clean and you're ready for paint.

[DJ metadelic]

Yeah bondo will only hold up for so long. I assume he did not use tigerhair, but just regular filler and mudded over it/smoothed it out?

Take some fine grit and re-sand. Search around, there should be some existing threads on this as well.

Good luck, we need pics to help though.

Trust me, up here-well pretty much everything's in bondo. Sucks. Bondo is fail.

[FAK_LAF]

I assume that the Bondo was used to fill in rust on rear fender like everyone else has stated. I had luck with using an angle grinder to cut out all the rusted material. Since you want to use as little Bondo as possible (Bondo is not good structural material, only finishing material), back the void that you cut out with fiberglass cloth and epoxy resin. It is very strong and bonds decently with steel. Fill the void with as much fiberglass and resin layers as possible, contouring to the body lines the best that you can. Be sure and allow the resin to cure between layers. Coat the outside of the fiberglass structure with Bondo to smooth the surface and match the existing body lines. Sand with progressively finer sand paper until the reconstructed area and existing sheet metal surface is seamless to the touch . Primer the reconstructed area and surrounding area. Wet sand the area and finish with a color that matches your paint. This is a cheap and decent looking fix without having a gigantic blob of Bondo that could crack and fall out for filling in you rust. Mine still looks great even after a winter of salty corrosive roads.