I always clean first before putting fluid film on. Your choice. I use a good citrus cleaner or any good degreaser. Then apply the hell out of the fluid film. Except exhaust and brakes. Stuff works awesome!! Been using it for years on stuff. It will stop any rust you have in its tracks. My 04 under carriage will look new forever.

So I've got a question for everyone. I've had any and all body rust repaired properly over the last few months, including a complete rear hatch, only to find out that we are going to (ahem) "need another big vehicle". So gotta get rid of my Gen 4 Sport that I've been working on building. I literally just put the FJ springs and adjustable Bilstein 5100's in LAST WEEK! I love my wife. Anyway! My question really comes down to this. Would you guys rather know that the rear axle and frame are solid, but come spring need a good wire brush and paint, or would you rather see it painted now? I hate the idea of just spraying the underside so it looks pretty, because it's so darn hard to find a good condition Gen 4 T4R in western NY because of all of the stinking salt in winter. Thanks and let it fly!

Hey have any pics of under your car?

how long have you been using FF?

Ill see if I can get any pics under it tonight. It looks new as the day it came off the factory line. Well mostly because it has never seen snow or rain even. Lol. Arizona 4runner. Ive used FF for years on other vehicles. Its very common around here with plow guys. I dont have any pics of previous cars ive used it on. But it will keep it like new.

I use Boiled Linseed Oil on all carbon steel ( frame, axles, etc...) . It will just penetrate through any existing rust and turn the metal back to black after a few days.

Buy it at Lowes or Home Depot in a can.

Can apply with a paint brush direct to metal, no reason to wire brush anything, it will soak through. Also , I put it in a cheap spray bottle, thinned with kerosene to enable spraying it into hard to reach areas ( no smoking ). My 2004 SR5 with 203,000 miles, mostly from the Midwest is free of rust.

Sorry to revive old thread but wanting couple questions answered. Is there any rubber under a 4runner which fluid film could cause problems with? Where not to spray to not affect brakes or exhaust. I'm thinking i can spray directly on muffler and my fancy exhaust tip which is already showing a little surface rust. Most videos i have watched peeps just leave the tires on and spray right up behind them (not seeming to be to careful they dont get it in the brakes) others pull all wheels off and mask around them. Just curious what most 4runner owners do

No issues with spraying everything on the 4runner. For obvious reasons you do not want to spray your brakes... Go ahead and spray your exhaust if you want a stinky smoke show for days. I always pull my wheels and wrap towels around the back side of the rotors and use towels around exhaust. I've been spraying lots of vehicles with fluid film over the years with no issues on any rubber parts. I spend a little more time on my stuff than most would. But that's the reason mine looks like new still. I pulled all my door panels and lift-gate panel and sprayed inside there also. Most of the engine compartment gets done also (gets washed off in spring). I always use a good degreaser/soap with a foam cannon in the spring to completely neutralize any salt on the underbody. Marine Clean works very good. I'm a little anal about my stuff. But living in Michigan you have to be if you don't want rust.

I used a gallon of fluid film on my 4runner about a month ago. I wrapped the exhaust from the catalytics back to the tip with aluminum foil to keep the fluid film off it. I evidently missed a couple small areas because now you can smell the fluid film cooking as it burns off the exhaust. FF smells bad to begin with, I would not recommend spraying it on your exhaust because then it smells even worse.

For the brakes, I removed all four wheels, took 8 plastic walmart bags and wrapped each brake/rotor/hub assembly with 2 of the 8 bags. Put one bag on the assembly from the front and one on from the back. This covered everything nicely and I didn't have to worry about where I was aiming the sprayer.

As for rubber, I'm not sure. I wasn't too worried about it except in the engine compartment. I made sure not to spray any hoses or anything there. But under the vehicle I sprayed just about everything. Can't say if that was right or wrong, this is my first experience with FF.

Thanks for the info. So prob best not spray exhaust. Any way to protect that or just replace when it rusts away. My 01 Tacoma rusted to oblivion and I want to avoid that. Actually have a fifth gen, search brought me here. I watched several videos and none seemed to avoid spraying exhaust, if it all burned off I suppose no protection there. Thanks again for info

Best way for exhaust protection is swapping out to Stainless Steel. Will take longer for it to rust out. Its mostly the heating and cooling cycle that speeds up the rusting process on the exhaust. And you can't change that.

Got rusty areas as well. Picked up some rust converter from eastwood and after applying that, I want to top coat it with por 15. Does that sound like it will hold up? I moved the truck to Texas so no worrying about salt anymore.

Here's what I did while replacing my front suspension stuff.

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I've never used Fluid Film here in Colorado, but it seems like a good product. The Por15 would work underneath to prevent the gravel sandblasting effect on leading edges. We always get surface rust underneath because the gravel used in winter has a sandblaster effect on the chassis paint. The beauty of the western states regarding rust is the lack of humidity. The roads of course are salted heavily when it snows, but one day later the humidity drops to 10% and all that moisture built up underneath gets sucked right out by airflow. There's no lingering moisture to keep working away at the metal, there isn't a constant freeze/thaw cycle day after day month after month.

Here in the Northern Salt-Belt:
Sheet Metal Rusting from the inside-out prevention is equal to Frame/Floor Pan rust treatment.
POR15 only solves half the problem, if treated early enough:
- once the auto-body panels gets perforated with rust cancer...expensive refinishing needed
- and the undercarriage is often the next to go
- after a decade, rust scale sets in and requires a ton of effort to remove

IMO - Fluid Film offers the best overall protection, if applied correctly.
- Fluid Film is a very decent wax-oil cavity spray, unlike Krown &/or Rust Check (aka water soluble product, that washes off quickly)
- not a fan of POR15 here...stuff has no shelf life, after can is opened
- if metal is clean, SPI Epoxy primer is my choice Southern Polyuerthanes, Inc. eastwood vs spi epoxy primer? | The H.A.M.B.

Pictured of my 2005 Jimmy 4x4 - that was my DD'er before finding my nice 2000 SR5.
GMC was previously oil undercoated for 12 years straight...product brand ?...and only has a few bad spots / so oil spray works.
- on the easy spots to undercoat, it has served this vehicle very well
- even the original brake & fuel lines, are caked like grease
- the rear left quarter area, now rusting from the inside-out...a hidden area, obviously missed of oil coverage, during undercoating
- after a mild etching, the dark colored metal is only half thickness (rust under paint area)...and will be removed
Now requiring rust holes be cut & enlarged, back to solid metal / and a steel patch be welded in or adhesive bonded.

Note - Gorlilla duck tape is good at protecting painted areas some, from wire wheel abrasions (on an electric drill).

Portions of the rear steel bumper was heavily corroded, and will be de-rusted prior to neutralized with a phos coating.
- such as Loctite Extend: Paint Over Rust with Extend Rust Neutralizer from Loctite Adhesives
Heavy scale on Rear Bumper is being removed with a carbide deburr tool, on a DeWalt 20V drill.
- tool has a flat bottom, like an end mill and is very effective

Rust Prevention has to be treated like a total package / rust proofing hidden areas, just as important:
- my dentist says, most people only floss the teeth, they want to keep...LOL

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What oil spray product did you use for the Jimmy? What is in that sprayer pic you've posted?