Fierwall rust

[vercingetorix]

While cleaning the firewall with a wire brush I uncovered a bit of bondo which I scoured out to reveal THIS!! There is nothing but superficial rust in the other classic rust spots, side drain boxes,fender wells ,spare tire or floor pans, just a bit under the battery tray, the tops of the fenders and this.

My qustion is how to deal with it. It is not positioned in a place or big enought to be a structural problem, it is situated right on the seam of the cowl drain box and the upper side of the passenger foot well.

So, POR15/cut and weld a piece or cut and braze a piece.

Also the tops of thefender wells have a vee shaped configuration that seems to trap water at the forward end, would it be wise to drill and intall a drain of some sort or will new fender seals cure this?

Need input.

Thanks.

H Houghton

[geezer]

In your pics you can see the bead rolled section that runs right through the rusted out area. Anything a few inches below the bead roll, which is there for structural ridgidity can be accessed from inside the car under the dash. Any damage above this would have to be cut out and repaired from only the engine compartment side unless you drill out the spotwelds and remove the cowl top sections. This illustration may help, but it is for a RHD. Just visualize the assembly reversed with the chimney on the other side for a LHD. I would cut out all the rust and replace the metal. Definitely more difficult to repair on a car that the dash is still in. You are looking at the tip of the iceberg. Rust settles in the seam where the cowl top sections join and are spotwelded to the cowl and quietly, gradually gets worse, absorbing & trapping moisture. After repairing the metal, sealing the seams, and ensuring the water drains, is very important.

Edited March 17, 2009 by geezer
elaborated a bit

[geezer]

It is easy to mask the damaged, rusted out area, but a permanent repair is needed in this location, that is sealed and will not trap water or allow water to enter the cabin.

I would suggest researching some of the panel bonding adhesives that are on the market today. This would be perfect for bonding replacement pieces that you can form and set in place, without any welding. No risk of fire. Totally waterproof too. I haven't tried it myself yet but I did have a long discussion with an ITW Devcon representative who had me sold on these adhesives by the time we finished talking. They are being used by automobile manufacturers to bond various panels and components together that in the past were spotwelded or wire welded. This way you can neatly cut out the rusted section from the engine compartment and expose/remove the rust damage inside and fabricate the required pieces and bond into place. The beauty of this is, the adhesive bonds metal to metal and seals the seam at the same time. Worth a look.

[vercingetorix]

Where would I find this stuff??

I was thinking of cutting the hole out,then cutting two pieces and welding them in centering them on the bead bar seen in the center of the hole,first the lopwer to make sure the cabin is sealed then the upper and reaching through from the top to seal the seam.

But panel adhesive sounds much simpler

[geezer]

I've never bought any or used it and only learned of it from an ITW Devcon rep who spoke only of using it in automobile manufacturing. I don't know what "home use" panel adhesives are available today, or the cost. I would be interested in trying some. Here is a link with some part numbers from GM you could inquire about. I just figure it's worth researching the different available products and I can see how it would help with a repair such as yours.

http://www.goodwrench.com/gmgoodwrenchjsp/gmspo/Chevrolet/HHR/2006-2008/25_Metal_Panel_Bonding.pdf

[240znz]

Had the same exact issue on my firewall. Body shop fabricated a patch and welded it in and applied plenty of modern seam sealer to the inside of the cowl. Trust me here, getting the sealer in is a PITA. Big cracked Kiwi hands are no match for small japanese hands for getting into tight places.

[a7dz]

I fixed that like these pictures. I cut the rust out. Bent and fitted pieces into the cowl area to hold the lower cowl panel . Sheet metal screwed them in place. Welded the seam so the piece in the cowl and the piece under the dash and the cowl pan all seamed into one. Welded the pieces in the cowl best I could. Same under the dash. Ground those welds flat and fit a another piece over them. Screwed it in place welded it up removed all the screws. Welded up the screw holes. Ground that all flat prepped the area for paint. I finished the inside of the cowl area with POR 15. I just poured it into the seams and let it set up. I sprayed the rest of the cowl area with POR 15 and have not had a leak in two plus years. After that cured I refinished the fire wall.

[vercingetorix]

A7DZ,

Nice. Your pics make me feel much better, the hole I will have to cut will be a good deal smaller. Mine is a bit higher and will take out a piece of the horizontal raised area and I'm not sure how I'll deal with that.

Did you use filler to clean it up? It looks great!

Also, does anyone know what gauge the firewall metal is?

Best,

H Houghton

[a7dz]

I worked the area as flat as I could get it and then I did the finishing touch with icing.