I am currently repairing fire damage in the rear footwells of my 92 500E. The car sat for 4 years. I was not aware how corrosive the fire extinguishing agent is that the fire department used. I have sandblasted from the inside and sealed with self etching primer. Now to the underside ( recessed area where fuel pump and filters reside ) the fire removed the undercoating and it rusted I am about to sandblast and also seal it. The problem is this when I sandblasted the inside It went through and left 2 small holes about 1/4" . Shouls I braze them shut , weld or epoxy repair then prime and seal. I plan to use Herculiner on the underside so it is completly sealed and should stop further rust development. The area gets covered with a fiberglass cover so it will have some protection. I plan to keep this car and when I can afford a lift will weld in new metal. Help.

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

Thanks for telling us about the corrosive nature of the fire extinguisher. I didnt know that. Had you know about this four years ago, would it have been relatively easy to clean that residue out as compared to having waited this long? Do you know?

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1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
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Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

Dee8go, I have a call in to the fire department and will follow up with the manufacturer. But yes if I had known i am positive that with a simple cleaning using the correct product ( my first thought would be baking soda & H2o ) i would not be where I am at this moment. I should have thought about this sooner since my schooling was an aircraft mechanic and had classes on the various extinguishers and the pros and cons. I kinda got sidetracked after the car went to a body shop at a local dealer to get an estimate it sat in there lot for 3 months before they said it was totaled ( I in turn priced out the parts and bought the car from the insurance company ) after they told me I would have an estimate in a few days. As most of us know the shops do not want to deal with fire damage because of the likely hood of comeback work.
My car is almost ready to change the fluids and fire it up. I will post a thread when this is all done as well as photos detainling the damage and repairs.

Alan

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

Your best off welding it, floors are structural on a unibody car. Even a small hole such as this is best welded. It should not need a lot of effort to do this.

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With best regards

Al

Al , I agree with the welding. At this point in time I need to get the car on the road for 2-3 months and then during the winter I plan to have a lift in my garage so I can properly address the issue and drive one of my 4x4 SUV's. It seems that the best route for me is to go ahead with the zinc chromate primer and then seal the holes with a seam sealer type product or silicone based caulk. This will keep fumes etc out of the car until I can do it properly and are both fairly easy to remove. Input ???.
Thanks for the response.

Alan

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )

CORRECT:
Floors are structural on a unibody car.


Welding is the only safe answer..


Have a wonderful day

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Use a seam sealer type product.

Do NOT use silicone based caulk, it will draw moisture/corrosion.

I agree about the structural rigidity of the unibody cars. This is in an area that is a curved reinforcing feature added to the stamping for the crossmember piece just below the front edge of the rear seat lower pad. I have built and restored aircraft ( all still A'OK per the fed specs FAR's ) so I understand your comment and appreciate the input. I was more curious regarding the rust and something to halt it's progression for a few months. I love this car and hope to have it for a long time. Thanks for the input on the silicone caulk. I am ordering the seam sealer tonite and will lay a seam friday. My driveway is being repaved tomorrow a.m. and my 68 caddy has a case of I"I do not want to start ", so I can't move it easily ( my driveway has a little problem with the grade ). Thanks again for the input, this a great group of enthusiasts and I always appreciate the help !.

Alan

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92 500E Silver 66k
82 Porsche 911SC 84K
68 Cadillac ( Gone Now )
03 Suburban Z71 200K
85 300SD 217k From Original Owner ( Dad )