Floor pan/frame rail/firewall joining location with rusted hole

[AdreView]

Guys,

 

How would one go about repairing a hole in the floor board where the frame rail, inner floor, outer floor and firewall meet?

 

I'm looking for step-by-step instructions so that I don't compromise too much of any one layer here, if that's possible.  Where the firewall seam begins to angle up from the floor there's 2 firewall sheets and what looks like a cavity in-between.  Is this a location where 3 pieces come together, plus the frame rail over the lower pan?  I can't seem to figure out or find schematics of this location in the FSM or anywhere else.

 

 

[johnc]

You are looking down into the frame rail through that hole. That section is actually two box sections running fore/aft, one on top of the other.

 

You need to:

 

1). inspect and determine the extent of the rust.

2) determine if the time and effort required is worth it.

3) cut out all the rust.

4) fabricate the replacement pieces.

5) weld them in.

6) grind the external areas smooth.

7) rust proof.

8) prime and paint.

[AdreView]

You are looking down into the frame rail through that hole. That section is actually two box sections running fore/aft, one on top of the other.

 

 

John, is the area from the seam above the rail 2 pieces?

I can stick my fingers up into a cavity between the inner and outer angled firewall section, is this normal/correct in design?

[savor]

Here are some pictures of what I did to fix a rust hole similar to yours. As you can see the rust went through three layers of metal- firewall, upper portion of the front frame rail, and the frame rail itself.

 

 

 

I also found out that the rust extended further down, sandwiched between the frame and the floors. Since I wanted to remove as much rust as possible, all of that had to go.

 

 

After the rusted metal was cut out, I fabricated a piece of metal to fit in the cut section. Wasn't difficult- just needed time to massage it in. This piece was later spot welded to the frame and seams welded. Will have to get around to griding it smooth.

 

I decided to ignore patching the metal at the top of the front frame rails. I did, however, use ospho and the eastwood internal frame coating in that area. I will probably spray some of this stuff inside the frame rails again once I drill access holes in the replacement frame rails.

 

 

Hope that helps.

Edited April 22, 2014 by savor

[johnc]

You need to cut the area open and find all the rust.

[AdreView]

 

 

Hope that helps.

Very helpful.

When you said the panels were spot welded then filled in was this all done by mig or tig welding?

[savor]

It was all done with a mig.

 

To clarify, the spot welds were done where the frame rail met the floor board. You can see them in the picture with the holes drilled in to the floor board. The smaller diameter drilled holes were used as an outline, for the cut off wheel, and the larger circular cuts were made for factory spot welds. The spot weld cutters can be found at harbor freight.

 

The seams around the replacement was welded less than a quarter inch at a time. You should skip around and take your time, enjoy a beer... or a couple.

Edited May 1, 2014 by savor