Firewall rust problem...

[nico]

I am trying to get my dad's 84 Silverado back on the road and am at a standstill.  The firewall has numerous rust spots from years of leaves laying on (and inside) the cowl. It has rusted completely through the outer skin down low on both sides of the master cylinder, behind the engine and to the right of the a/c box. Most of the rust is concentrated around the pinch seam, but is also coming through the upper seam.  What can I do to fix it and keep it from coming back? 

[VileZambonie]

I would look for a rust free cab.

[hotrod24]

got any pics man

[nico]

Sorry, I don't have any pics yet. I will try to get some in the future. I thought the rust was only in single layer steel, where I could easily patch it, but it is through several spots and into both layers... I may just have to find another cab.

[dunedigger]

The last cab I used had the same problem but was rust free on the underside so in my opinon was worth fixing, especially where I am from.  It was a lot of work to get rid of it.  Once I got digging into it things got a lot worse but is all good now.  I decided the whole problem was whoever caulked the seam at the factory was asleep for about 6" of the seam and let water and leaves under the caulk.  I spent a lot of time digging the caulk out before I got started, very time consuming.  Couple pics of my buddy helping me weld it up and one of it done. 

[hotrod24]

nice work man very nice

[nico]

Those pics are very similar to my problem, but I also have very small holes along the horizontal seam and down where the floorpan meets the firewall, near the center of the panel.  I checked with several body shops that I have used in the past, nearly all recommended replacing either the whole panel or the entire cab.

[hotrod24]

it depends on how much work you want to do how is the rockers and the cab corners? but if they are good i say fix the rust on the firewall but if they are bad get another cab because that may be to much work that you want to do

[dunedigger]

Good cabs are getting hard to find here in Michigan. 

[nico]

The rockers and cab corners are fine, but in Oklahoma cabs are very easy to come by. I have an 85 LWB for parts already and have access to at least six more.  I'm going to have a buddy that's a body man come look at it and give me an educated opinion.

[80stepsideguy]

I had some similar problems especially since florida`s coast eats up some metal as well.I been on this cab for quite some time here n there and here are some pics i had to deal with.








All the rust is finally fixed, and i welded up the pinch seams nd removed all that seam sealer junk  and used some USC all metal and now i`m here till hopefully in a week or 2 then be done with the firewall...

[trucknoob]

I'm going through this same problem right now with mine. How did you go about forming the metal in the firewall area that was concave for the engine. Did you just tack the piece in and use a body hammer it into shape or what ?

[Oliver]

All the rust is finally fixed, and i welded up the pinch seams nd removed all that seam sealer junk  and used some USC all metal and now i`m here till hopefully in a week or 2 then be done with the firewall...

Why did you fill one hole for the heater box and not the other?