does this rust start from the inside or outside??

[Nasty-LSX]

Im looking to buy a 87 short bed to convert to a stepside. I found a decent 1 where the only rust is thew top of the cabin. How serious is this. does the rust start from inside the cabin area or is this a normal rust area? thanks.

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Well i went outside to look at my 85 and there is a seam there. Seems the the 87 has bondo over the seam at 1 time.

 

[firebane]

That rust is from someone poorly trying to get rid of the seam line along that area and now it has rusted like crazy.

Someone probably just used a ton of body filler and didn't prep or paint it properly.

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[Georgeb]

You will have to get all that filler off of there to asses the extent of the damage but that looks bad! Does that cab have clearance lights? I ask because I was trying to figure out how the moisture could be getting inside if it is rusting from the inside out. Either way you need to cut it out and replace it.

 

[MadOgre]

Bondo is supposed to be applied to bare metal. Bondo always rusts out panels because it is applied to bare metal !!! Bondo is garbage !!! always has been.

POR15 bare metal then apply Bondo. It is the only way to avoid the bondo induced rust.

If applied properly it will take 10-15 years for the Bondo to rust out panels but it always does regardless of how well it is applied or quality of Bondo.

Supposedly the POR15 then Bondo method should never rust. Leading would be a better alternative then bondo. But who knows how to do that? lol

BONDO SUCKS THE BIG ONE !!!

 

[Georgeb]

Leading. Now there is a skill i would like to aquire!

 

[smoothandlow84]

Lead fill...problem solved. My dad's an old school auto restoration guru. He passed on to me how to lead fill rather than bondo. Its toxic, and definately a dissapearing skill. Now a days its all about quick fixes, turn around and profit. Bondo has its place in bodywork, but to do it right is the key. I was taught that any metal flaw more than 1/4" is not to be filled. Panel replacement instead. Bondo is for MINOR surface imperfections, yet most people will weigh down a metal panel with bonda as a cheap quick fix. I always bring a magnet with me when kicking the tires on a resto project, especially one thats been painted.

If the magnet don't stick......the bondos too thick!

 

[donmateo]

^Great advice! I think everyone should do it. Otherwise you may end up buying a bondo-box on wheels!

 

[bucket]

Bondo is supposed to be applied to bare metal. Bondo always rusts out panels because it is applied to bare metal !!! Bondo is garbage !!! always has been.

POR15 bare metal then apply Bondo. It is the only way to avoid the bondo induced rust.

If applied properly it will take 10-15 years for the Bondo to rust out panels but it always does regardless of how well it is applied or quality of Bondo.

Supposedly the POR15 then Bondo method should never rust. Leading would be a better alternative then bondo. But who knows how to do that? lol

BONDO SUCKS THE BIG ONE !!!

Alright, here we go...


I could not possibly disagree with you more on this one. But first of all, let's get one thing out of the way- "Bondo" brand of filler does indeed suck, but there are several other modern quality fillers out there that DO NOT suck.

Body filler itself DOES NOT cause rust. I repeat, body filler itself DOES NOT cause rust. Rust is caused from improper application of filler, improper use of filler, low quality filler, or a combination of all of those. Plain and simple.

I do agree though that leading is better (but most anything built in the last 30-40 years doesn't have sheetmetal thick enough IMHO) but even better than that is just good old fashioned metal finishing. Putting filler over POR15 is a bad option too, and besides that, POR15 really has no place at all on an exterior body panel.

If you care to have a discussion, I'll gladly go into detail on why I said everything above.

 

[bucket]

And many magnets will stick even if the filler is 1/4 inch thick. One of those floppy refrigerator magnets work the best for finding filler.

 

[MadOgre]

Alright, here we go...


I could not possibly disagree with you more on this one. But first of all, let's get one thing out of the way- "Bondo" brand of filler does indeed suck, but there are several other modern quality fillers out there that DO NOT suck.

Body filler itself DOES NOT cause rust. I repeat, body filler itself DOES NOT cause rust. Rust is caused from improper application of filler, improper use of filler, low quality filler, or a combination of all of those. Plain and simple.

I do agree though that leading is better (but most anything built in the last 30-40 years doesn't have sheetmetal thick enough IMHO) but even better than that is just good old fashioned metal finishing. Putting filler over POR15 is a bad option too, and besides that, POR15 really has no place at all on an exterior body panel.

If you care to have a discussion, I'll gladly go into detail on why I said everything above.

Im not too proud to be corrected so Im all ears. I've been corrected before lol

 

[MadOgre]

I have applied POR15 to bare metal exterior panels before then etching primer, regular 2K primer and then paint with no issues at all. So Im curious why you say that POR15 shouldn't be applied to outer panels and also why no body filler over POR15?

 

[Nasty-LSX]

I have applied POR15 to bare metal exterior panels before then etching primer, regular 2K primer and then paint with no issues at all. So Im curious why you say that POR15 shouldn't be applied to outer panels and also why no body filler over POR15?

I have done this same exact thing with great results. Results are still great with no peeling. its been 6 years and still holding.

Im going to pass on this truck. The cab door jams look the same as the top of the cab, just not as bad.

 

[MadOgre]

I have done this same exact thing with great results. Results are still great with no peeling. its been 6 years and still holding.

Im going to pass on this truck. The cab door jams look the same as the top of the cab, just not as bad.

You have heh? Good to know! I did my front fenders like that 2 yrs ago and not even a hint of anything they look like I painted them yesterday.

The guys at POR15 swear that Body Filler will adhere great to POR15 I haven't tried that yet but I plan on doing that with my upcoming build I have planned.

If somebody knows why I shouldn't then I would like to know, but I cant see why it wouldn't work?

It all depends though on getting a good bond for the POR15 to the metal, cause if you have issues there then your screwed for every step after that too! That's why you need to follow the POR15 instructions to a T !!! But if you have a good bond for the POR15 I cant see why the Body Filler wont work well. Everything would need an etching or epoxy primer after the body filler anyways so that should seal up the filler good on both sides. I would think that way it would damn near last forever.

I have a frame that I am cleaning up and someone sprayed it with just epoxy primer and it held up better then anything I have ever seen other than POR15. Its probably the only reason why the frame is in such good shape!

 

[MadOgre]

I would pass on that cab too! Its impossible to get at the back side of that rust with out cutting and chopping which makes the cab not worth it then

 

[bucket]

I have applied POR15 to bare metal exterior panels before then etching primer, regular 2K primer and then paint with no issues at all. So Im curious why you say that POR15 shouldn't be applied to outer panels and also why no body filler over POR15?

I guess I should have clarified that the POR15 thing was just my opinion. POR15 is rather thick, and to get filler to stick to it, you have to sand it first (obviously). Sanding POR15 doesn't work out the best because it doesn't like to feather back at all and the edges tend to peel. It also clogs up the sandpaper which is very annoying. So to get a smooth surface once the filler work is done, you need a substantial coat of primer to sand it all smooth. Once that is done, you basically have primer acting as a filler over a poorly prepped surface and there's a good chance shrinking will occur later on, causing a halo in the paint around the repaired area. Coating an entire panel with POR15 is something I've never done, so that might be why your results have better, cause you don't have to feather it.

Besides all that, I think that if you need POR15 because the rust can't be sanded off, then that area of metal really needs to be replaced. Having rust come back through a nice paint job bites the big one. If it's an inner fender or frame or something then it's fine, if the rust starts showing though, just put more POR15 on top of it.