I've been following all the frame rust threads and have yet to see anyone bring this up, forgive me if I missed it.

When I bought mine 2 years ago, it had an inch of dirt built up in the internals of the frame in the middle section under the doors, or between axles. The small drain holes in the frame were plugged with stones and the dirt and dust had built up over who knows how long. This mess holds the damp and I suspect contributes to the rust from the inside out. Always wet in there.

I bought a cheap garden hose and cut a 20' piece that I could insert in the frame from the back under the bumper. You can snake the hose almost all the way up to the engine from there. Then I turn the hose on full blast and let it run, slowly pulling the hose back out over the course of 10-15 minutes.

The amount of mud and pebbles I flushed out the first time had to be seen to be believed. Likely had never been done since new. I now do it spring and fall and still flush a noticeable amount which accumulated over the last 6 months. (I do drive a fair amount of gravel.)

Stick your finger in your frame in a few places to feel around for dirt. Once you have the hose it's a quick and easy thing to flush out. Certainly worth doing before you spray any rust proofing inside the frame.

Can't hurt anything anyway. Good luck.

Good advice. Best rust prevention is just awareness of the truck. If you only look under every few years you might be in for a shock.

Don't be concerned too much about the frame rust, if you notice it's all just one user bumping every rust thread in the forum's history and trying them to file a complaint with Toyota, probably to get his recalled and fixed for free or something like that. Toyota's not going to recall a 13-19 year old vehicle though.

I'm doing something similar but the frame is blocked on my truck from the rear... theres a circular bar that runs through the drivers into the passenger's side frame rails and will not allow me to get my PVC pipe in. Is there any trick or a sweet spot? For sure cannot get anything passed the rear axel let alone all the way to.the engine.

Good thinking man!

There will never be a 4Runner frame recall. US built frames only up to 15 years old. If you live in the rust belt holesaw larger drain holes in your frame in the low spots and coat it with something inside and out.

Where did you actually insert the hose and snake it forward? I've gone under and can't find a spot to insert a hose

Old late reply, sorry.

The frame channel is open right at the back. Access it from under the rear bumper. If you have a hitch mounted it might be hiding things.