Rust on "brand new" 4Runner

My girlfriend bought a 2024 4Runner with 400 miles on it in Jan 2025. Has since put 2,000 miles on it and noticed a squeeling noise when braking. Took it to dealer and they said rust was on front brake rotors. They fixed supposedly, but I was curious and got under the car to check for other rust. I attached pics, should we be concerned about this? And if so what can be done?

 

Not sure about those specific pieces but I would definitely definitely get the frame treated with fluid film being so new. Spend enough time here and research frame rust.

 

It's cast iron - rust will appear overnight on brake rotors and it'll be gone the first time you hit the brakes with any gusto.

As for the rest of it, rust is normal on unpainted surfaces and it's not going to be an issue on large, cast parts. If it bothers you, wire wheel it and paint it. It's very normal on cars.

 

That's all normal. You can undercoat it with Blaster, fluid or something comparable, or find a shop that does it. St. Louis has Krown St. Louis, they charge around $180 to cover the entire truck. You should be able to find a shop wherever you are.

 

I would argue differently. I think that is excessive for a 4 month old vehicle. Even the pin of the castle nut is corroded. And the corrosion on the knuckle of the drive shaft is inconsistent. I’d have them look at it and voice your concern. Maybe they will coat it for you.

 

Depends on what part of the country they are in, salt starts eating steel fast.

 

Mine had that when it was new. I wire brushed most of it and it never came back.

Correction, I used scotch bright rather than a wire brush.

 

Those rust spots are normal.. go look at a 2024 Tacoma new on the lot, you will see the same

 

Yes, as the others have said. Also normal to find the rivets that hold on the fuel door show evidence of corrosion.

Curious to know if the bolts used to install the rear seatbelts still poke through the rear wheel-well coating on the 2024 models?

https://www.4runners.com/threads/2022-4runner-fuel-door-hinge-rivet-rusty.24204/page-3#post-545494

https://www.4runners.com/threads/do...lt-poking-out-into-the-rear-wheel-well.27224/

 

It is fine. Get underneath other units of similar time and you will see the same. Cast iron is what's showing not rust. But check with others to make sure you feel good.

 

That’s how they all are. For some reason they don’t paint those parts. Probably to keep a smooth mounting surface.

 

I noticed similar with our 2024 and was concerned at first… finally realized I’m expecting perfection.

I live in CO (not rust belt), I did coat the bottom of truck with wool wax (clear version) and will probably touch up next year…


I’m really not sure how I will wash the underbody, but I hear some people use an oscillating sprinkler or simply a pressure washer

 

Those same parts were rusted on my 2019 right off the boat from Japan.

I have been hitting them with rust converter over time.

 

The Car Care Nut has shown a few different models that are not being coated like they used to be. I had the same thing with my 2023. 4 miles on it and fresh off the truck. It was in similar spots, it even had a few spots on the weld joints for the frame and some rust on the exhaust lines and the muffler. Not just the flange areas.

In comparison, I bought a 2014 with 87,000 mi on it and it didn't have rust on it anywhere near the level where my brand new car did.

My 2023 also was not completely primed and painted in the engine compartment. There was bare metal underneath the plastic cover over the radiator area.

 

I worked as a service advisor at dealer when I was young. The absolute worst job I ever had.

 

My 2023 taco had surface rust on those same areas. I just used sandpaper by hand and then sprayed enamel paint. Then like others said get woolwax / fluid film on whole truck.

 

Mine, within 1 month of ownership

 

Welcome

 

Thanks for all the replies, they put our minds to rest. Will look into the undercoatings that several people mentioned.

 

I wouldn't be surprised if these parts were rusty before it even made it the US port.

With any humidity, bare steel will rust literally overnight.

 

My other car has never seen winter, garaged all year, and still got surface rust on bolts/connectors made of cheaper metal before I Krown treated it. Moisture is what it is.

I’m very anal with maintenance and Krown treat all my cars but I wouldn’t worry about minor surface rust on small replaceable parts. Frame, body, and larger components (like the axle housing) would concern me.

But would definitely do an oil-based undercoating annually if you plan to keep it fresh for many years. I immediately did my ‘23 right after I picked it up from the dealer, haven’t washed the undercarriage since, and it looks like new underneath after its first winter daily duties.

 

Metal rusts, and some rust isn't bad, i would even say it was like that as soon as it came off the boat. I don't understand why someone would think rust like that is bad, or that having rust that soon isn't normal. Its going to take many many many years before it even matters.

That said you can be proactive about rust if you plan on keeping the 4Runner for 200k+, like Blaster, fluid film or something comparable to help protect parts.

 

As mentioned in Post #4 above. If you have a Krown Rustproofing location in your area, please consider them. With 4,000 miles on your new rig, now is the time to do it. My first application was at 600 miles. Then repeat once a year. Here is a Link that I posted for my 2021. This was the third application. Photos taken while 4R still on the rack just after application applied. This is what the under carriage looked like after 3 years and about 20,000 miles. Not bad. They even do under the hood on the fire wall and wheel housings. The treatment does not effect electronics. HINT: Lower your spare tire and leave it at home so they can access that area. Onlytakes about 1 1/2 hours. You can wait for it. Price is very reasonable and cheap insurance down the road.

https://www.4runners.com/threads/krown-rust-proofing-results-year-3.40429/

 

Decades ago I found a marine grade rust-lock liquid I used to treat steel and cast steel engine parts on in the ocean sailboats. Paint only only did not last long. I treated these bare steel parts or parts where rust broke thru the existing paint with rust-lock and overnight the rust was chemically converted to a grey material. I either left it, or painted it with a small brush from a half pint of Rustoleum. It would not show new rust for a very long time.

 

I also Krown Rustproof my ORP. After 3 yrs she still also looks like new under a nice buildup of oily dirt. And yes I'm OCD about 4Runner under carriage rust living in a salt belt. So I pull the skids as well as the spare before hand. I removed the foam strip under the radiator. It holds salty water and contributes to the rot of the lower rad support and tow hook area. Yes I know it's there to direct air flow. I tip the guy with the spray wand to blast the inside of the boxed frame. Tell them you don't care about driveway drips and they will flood it. I have it done in the late summer while it's still hot so it has time to creep and let road dirt stick to it before winter. Dirt helps it from washing off and acts like a sponge for the next time. I have a case of their spray cans for spot treatments like the KDSS accumulator. Only thing I've noticed from the Krown is a bit of swelling and softening of the front inner fender shields that protect the sides of the engine. Not a big deal. Way better than doing nothing.

 

Good tip about the skid plates. After almost 4 years there is still no rust on the heads of the bolts, usually one of the first places to show rust. My 21' will get it's 4th treatment this August. I'll report back again with photos.

 

Amen. I do the exact same thing. Every dirt particle is more surface area for product adhesion. And 16 years of Rust Check/Krown filth accumulation helps at keeping the rodents away.

 

The atmosphere over the ocean is corrosive. When I used to ship electrical equipment by sea we always specified, "Pack for ocean transport."

Otherwise all the hardware would be corroded before the gear hit the project lay-down yard. The corrosion would be just surface rust and did not affect the fit for purpose of the gear. But it looked bad, so we paid extra to keep it pristine.

I would not worry at all about that kind of surface rust being a detriment to vehicle longevity...

 

Nor would I. But seeing as these 4Runners come from Japan via slow boat I guess some salty air gets to them before they even arrive here in North America. When I took delivery of my '22 I could see areas on the frame in front of the wheels where the paint was rubbed off to primer and bare metal from tie downs. Maybe car carrier maybe slow boat don't know. But I did scuff and repaint those areas.