The panel right behind the passenger door has a hole in it from rust. I need a little advice on the best way to patch it. I was told to use Bondo body filler and fill in the hole but it just runs down the inside and does not fill in the hole very well. should i use something as a back until the bondo fully hardens or something. the hole is about 7 inches long and about 3/4" wide with one spot that extends to about 2" wide. i have a pic if needed

Any advice is appreciated

thanks

My uncle told me about a trick if you put bondo on the smooth side of the sand paper then stick it on let it set then carfully peel the sand paper off it should leave a nice smooth surface.

Edited April 11, 201213 yr by AKghandi

i've seen bondo falling apart (have one right now) with mesh/screen behind it that was obviously there to hold it in place.

 

putting in new metal is ideal for big holes, but obviously that's not a good fit for everyone.

this is the hole i am trying to patch. A piece of trim goes right there so I will need to be able to drill holes to attach it

Put some fiber board behind it then cover with bondo then screw the trim through to the fiber board.

Or just cut a strip of sheet metal, stick it on the inside and bondo over it.

cutting out the entire rusted area and welding in new metal is your best bet. Although, not everyone knows how or has the tools to do so. The next best option would be to cut out the rusted area, and then put some fiberglass mat onto it, rough shape it, skim it with body filler, etc.

...

Edited April 12, 201213 yr by tundrabrat

Unfortunately that hole is too big for bondo alone, even with screen as a backing.

 

1. Grind or cut the bad metal out.

2. Treat the rusty area with a type of rust killer.

3. Go to the local hardware store, buy some 18 or 20 gauge steel or aluminum and a rivet gun

4. Cut the metal to fit with a 1/2 inch over lap.

5. Drill. Holes through the metaland your panel (you may want to tape the patch in place while you drill.

6. Rivet the panel in place.

7. With a hammer tap around the perimeter to make a slight indention.

8. NOW you can add your bondo, sand, prime, paint.

 

While I will always recommend welding first, this is a good long lasting repair that is an easy afternoon/day project... and it wont rattle out when you go over the first bump (:

+1 tundrabrat

i dislike bondo though, i live in the salty north east and when i need to patch something, I Grind, Wash with alcohol, Paint, and Rivet the Aluminum sheet (wont rust) with aluminum rivets on, but I don't mind its appearance

making sure the metal is exact fit and always thinking of water travel

i just did this to my 85 GL Hatch

inside the rear fenders and underneath the doors and the doors themselves

underside and weel wells got some rubberized undercoating

Edited April 13, 201213 yr by blindrummer

Click on my Avatar and You'll Reach a Link to a Complete Writeup, Plenty of Pictures, on the Subject.

 

http://www.ultimatesubaru.org/forum/member.php?tab=visitor_messaging&u=17344&page=2#visitor_messaging

 

Kind Regards.

cutting out the entire rusted area and welding in new metal is your best bet. Although, not everyone knows how or has the tools to do so. The next best option would be to cut out the rusted area, and then put some fiberglass mat onto it, rough shape it, skim it with body filler, etc.

 

+10 - if you dont know how or have the tools for welding in good metal, fiberglass is a MUCH better choice than bondo.

 

here's a few pics of a repair job done with fiberglass - rust was cleaned up as much as possible, then treated with a rust killer, then the whole works fiberglassed. It was still holding up several years later when we sold the car. never did paint it...

 

Getting started

 

Getting all mounting holes cleaned up & filed

 

Reinstalling hardware

 

and how it looked complete (but unpainted)

I like the rivet idea!

I've done the rivet thing before. Just make sure you seal up the seam between the two metals really well. Put silicone or something. I did the rivet thing and it rusted out and fell off in two years. So I just up and welded some sheet metal. IMO the only proper way of doing it.

 

Regardless what you do though, two most important things are: Cut out all the rust completely. Rust is like cancer. If you repair over rust it WILL come back. It needs to be cut out.

And seal it up once you're done. If the repair isn't sealed up nicely water will get in and rust it out again. Especially if it's bondo, that stuff is evil and holds water.

Unfortunately that hole is too big for bondo alone, even with screen as a backing.

 

1. Grind or cut the bad metal out.

2. Treat the rusty area with a type of rust killer.

3. Go to the local hardware store, buy some 18 or 20 gauge steel or aluminum and a rivet gun

4. Cut the metal to fit with a 1/2 inch over lap.

5. Drill. Holes through the metaland your panel (you may want to tape the patch in place while you drill.

6. Rivet the panel in place.

7. With a hammer tap around the perimeter to make a slight indention.

8. NOW you can add your bondo, sand, prime, paint.

 

While I will always recommend welding first, this is a good long lasting repair that is an easy afternoon/day project... and it wont rattle out when you go over the first bump (:

 

 

This is the way to go. substitute a welder for the rivet gun if you have access to one. Maybe use an epoxy seal if riveting. Then grind down the rivet heads and use body filler.

 

Woth body filler, the idea is to use as little as possible. Big wads of it will swell and fall off. It is not meant to be a structural material, but rather to be applied thinly to feather seams together and fill small imperfections.

 

Cutting and welding is the way to go. Here is what i did for my rust:

http://www.ultimatesubaru.org/forum/showthread.php?t=119353&highlight=3door&page=6

grind edges to the metal (inside and out),Bondo-glass both sides with fiberglass mesh on the inside of the panel(1/2 inch larger than hole).