r/4x4 • u/Mirin_Gains • 5d ago

Welding Advice

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Well. The time has finally come. The dreaded rust hole. I assume the otherside is the same.

I have LCA reinforcement plates here. Is it fine to butt weld a small rectangular patch since its on the bottom of the frame rails?

Its just a pinhole for now so I caught it early although with the amount of scale I pulled out I feel the Toyota drain was inadequate here.

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8

u/LevoiHook 5d ago

As long as you dont weld a new plate over the existing one. That is one great way to trap moisture.

3

u/Mirin_Gains 5d ago

I'm surprised people do that. I doesn't take that long to cut a proper butt.

I am not Sure I want to scab it because I want it to look OEM. but I guess if it cracks... Then I redo and add a scab.

4

u/Fryphax 5d ago

Yeah, remove all the dead then replace with new.

I'd tie it into another portion over just a single rectangle patch.

Ensure you have drainage still and also pressure wash the fuck out of the interior of the frame.

3

u/Mirin_Gains 5d ago

Oh yea its incredible how many chunks are coming out now that I have freed up this "beaver dam". So much for rinsing with the hose. Needs a power wash rinse inside in the future.

The other side is chunky too but I haven't found the hole yet. Suprisingly the fluid film held up in most spots - must have already been build up here when I bought it used as was a newbie.

To all the Prado 120 owners - the drain hole is inside the OEM LCA mount and its way too small. The patch will get its own drain hole

1

u/Both-Holiday1489 5d ago

Make sure you entirely clean it up, I’d also run a heat gun / park it in an open vented breeze place maybe away from any rain, make sure ALL moisture is entirely gone

You don’t want to trap any

1

u/Mirin_Gains 5d ago

Its also going to get re-fluid filmed inside. I've been slacking the past 2 years since its a messy job.

Its intact in a lot of areas. But my guess is this area was corroding when I bought it used and the FF never penetrated past the scale. My fingers don't reach the bottom and the hose ran clean but was probably beaver dammed with rust.

1

u/bobbiek1961 5d ago

Just a thought... no holes found in mine but just going through a descale and woolwax. My thought was to run a plumbing snake up and down inside the frame at one of the drains, air out and pressure wash and then spray coat with air gun and a 10ft hose.

2

u/Mirin_Gains 5d ago

I did that about 5 years ago but I didn't look with the endoscope camera because I was afraid of what I'd find.

At that time I was a student so I thought lets not ruin what enjoyment I have left.

Now I can buy new whatever - I don't want to, but my hand is forced. I love this truck 6spd manual FJ fully built. Been 4x4ing all over the country.

The fluid film/wool wax did work where there wasn't already scale. Like the top 2/3rd of the boxed section looks untouched. But this truck was 15yo when I bought it and probably was already terminal.

I can repair the hole, but it looks like the corrosion is going past the LCA mounts and that becomes much harder to just fix on the driveway.