How to rix underbody rust

At some point during the California rains this year my 4Runner underbody became flooded (when a storm drain flooded on a hillside street parking spot), and the skid plates and some struts, and other parts of the underbody became rusted. I filed a comprehensive insurance claim but it was denied as they don't cover rust even from flooding.

My questions: how can I fix and prevent this from happening again and how much have I reduced the overall value? Toyota mechanics say nothing mechanical was damaged but that's hard to believe. Would sanding and painting with rust proof paint work? I'm quite depressed about this. any advice would be appreciated, thank you!

 

Wool Wax or Fluid Film

 

They can shoot it with dry ice and do a undercarriage paint. New again. Then coat it with rust protection lube. Before every winter blast the undercarriage with a can of lube. If you do it yourself respirators and eye protection. Can't afford the dry ice. Wire brush it then paint.

 

While greasing my U-Joints this weekend, I noticed a small patch of rust on the rear driver side lower shock mount. I just sanded the rust spot clean and squirted some black rattle can paint on the area. It’s unusual to have rust in my location, but if I see a spot, that’s how I address it.

 

↑ These guys got it right, good advice. I think your mechanic is right it doesn't sound that bad to me, try living in Canada every winter!

 

Can you post pics so we know how bad this is?

The sewer water may have things in it that accelerate corrosion. First thing I’d do is spend an afternoon rinsing the undercarriage with fresh water from a garden hose. Use plenty of running water inside the frame rails, crossmembers, body mounts, and other nooks and crannies. Basically you need to have enough water rinsing over everything to dissolve any dried contaminants that are sticking to the frame. They sell products you can mix into water to dissolve salt (usually sold to boat owners), which might not be a bad idea to use in case that sewer water was backwashed with sea water.

After that, you can spray fluid film, woolwax, or any other metal preserving oil over the frame, inside crossmembers, etc.

As far as diminished value, judging from the rusty frames I’ve seen on used 4runners around here, probably zero. People that know about rust simply walk away from bad ones. That leaves tons of other people paying top dollar for them, and there seems to be plenty of those people around.

edit: unless you had something extremely corrosive in that sewer water, you probably only have surface rust. I’d spend your time rinsing and coating. Sanding and painting are only going to be in places you can access, but there would still be corrosion risks in places you cant see or reach with your hands.

 

Yep sure. Attaching here. Looks like a lot of this is dust that can be cleaned off, but a lot is rust.

 

It looks like surface rust. Rinse out as described above with water. Get a bottle of that salt dissolver for good measure.

I would take the skid plates off to make sure you dont have junk behind them and so you can rinse off under. Use light water pressure near sensitive areas, and put the nozzle on “jet” setting to spray inside the all the little holes on the frame side rails until it runs out clear. Touch the skid plates up if you want. If you have kdss, clean all of those components very well!

If it really bothers you, I could see sanding rusty spots for cosmetics, before coating it with a grease/oil product.

 

OP mentioned an overflowing storm drain - I saw nothing about sewage. I guess there could have been some of that, but storm drains usually are for diverting overflow from excess rain water.

I don't see anything in those photos some wire brushing/sanding + painting wouldn't fix. Also, if those places were rusted from the recent events, on a 2-year old 4R in CA, treating those as described above would be sufficient. CA vehicles don't require winter treatments to prevent rust. Unless, of course, the recent rains become more prevalent, and the possibility of further flooding exists.

 

get an inspection camera and inspect rust inside frame. not possible inspect rust in-between welded parts, but fluid film will protect there

 

I would say that truck looks normal.

 

Good grief

Yeah I wouldn't worry to much about it. If it bothers you that much, go under sand the rust, then paint it black.

 

Hey OP

i looked at your photos. That all looks fine to me. What i’d do:

• Drive to a self-serve carwash and rinse the whole undercarriage to get rid of grime, oil, and residue
• Go to home depot and grab 3-4 cans of black rustoleum spray and one quart can of brush on paint.
• Go to the taco shop and get a burrito.
• Bring burrito home. Eat it, while i wait for the undercarriage to dry out and cool off.
• wire brush any loose rust scales, then spray and brush EVERY nook and cranny with rustoleum.