I had my car on four jack stands to do my front upper / lower ball joints and a tire rotation so I decided to take my mechanic creeper for a spin under my car to inspect the chassis.
Though my car sees almost no AC-usage year around and I do at least two underside washes a month in the winter there was some rust starting on the passenger frame rail exactly were the brake / fuel lines clip to the passenger frame rail and a bit on the opposite side. But that was minor surface rust at least that's easy to deal with.
However the biggest issue I noticed was a rust spot on the driver frame rail, it wasn't at the frame rail seem like I saw in the pictures on this thread, it was almost a bit downward at the frame rail hole almost the one that is parallel to the transmission drain plug (I happened to be checking my transmission fluid level too this long weekend). Nothing is attached there obviously and it was starting from the inside it seems.
There was a very small rust spot on the outside side of that driver side frame rail that was starting at the opposite hole. But it was mostly surface rust.
After hammering all the flaky rust on the inside rust spot on the inside of the driver side frame rail which became as wide as a couple of golden dollars and as long as two and half quarters. It was in the middle and not on the edge at least.
I decided that the structural integrity doesn't seem to have been massively altered in a dangerous manner and I'm not willing to dump hundreds on repairs. So for the time being I decided last weekend to do it myself while the car was on jack stands.
I brushed cleaned all the surface rust that I found on the bottom on all frame rails, brushed clean and painted the brake lines as well. Then hit everything I could inside and out with a couple bottles of brake clean to remove debris.
I had a new can of Rust-oleum Rust Reformer on hand which allows one to paint over a clean semi-rusty / rusty surface which has been at least cleaned of debris.
So I sprayed that Rust Reformer heavily inside and outside of those three major spots that I had metal brushed to near bare metal and some rust. Then I sprayed the rest of the front half of the car with the leftover after of course brushing clean what I could.
All those major areas I sprayed inside and out three times to make a coat well what I could. Then that major hole on the driver side I wasn't sure what to fill it up with, I was running out of time, I had a Loctite silicon tube handy so I filled the heck out of that frame rail with silicone caulk to seal it on the inside. May have not been the best thing but I wanted anything that seals it and that's what I had on hand.
After emptying half a tube of silicone on that hole and perfectly smoothing the surface. I did a couple of thick coats of self-etching primer all over the Rust-oluem painted areas. After it dried I sprayed painted a couple of coats of paint followed by a couple of coats of enamel. I basically emptied my arsenal of old spray cans on that son of a gun underside. Then I idled my engine for a while to bake that finish and now I plan on inspecting it every couple of weeks to see if any of this hack job of rust proofing is failing.... I'll know for sure once winter comes.
While I was at it, I metal brushed and cleaned the transmission support and the front subframe and painted those as well with the Rust Reformer, self-etching primer, paint and protective enamel.
I spent a good 3 hours on that job and I hope I at least have stopped things from going further than this.
I think I need to get my hands on some very high temp silicone in a caulk tube so I can fill all those frame rails of this car up to at least seal them from air and water. That's my working theory at least, since only one rail has been compromised a bit, it's not too late to pack those rails to the brim with high-temp silicone, at least salt and moisture will not find a good spot to go from there except away from the rails which have been protected from surface rust.
Someone correct me if what I did above is futile or there is method to my madness or if I made things a bit worse with that silicone filling.
After almost 150 miles of driving everything seems good so far, that hole which I assumed would cave in no time due to the exhaust heat is still holding up strong, when I have time I plan on making a metal plate that I can weld to shut it for good, but for now the silicone is holding up.