Spraying Inside Door Cavities

What do you guys spray inside door cavities? I keep reading on wax type products some say even POR15 while other day talk fluid film.

I noticed some slight surface rust on the inner door lip/edge on the bottom. Which makes me believe there is some rust potentially within the cavity, but I’m not sure is fluid film the right thing to apply inside the cavity with existing rust or should a rust converter be used first and then wax/fluid film?

I’ve also seen videos that these rust converters are gimmicks and don’t really even work… which makes matters worse

 

I've never sprayed anything inside the doors - is that a thing?

I've probably got some dust, pollen, and a little rain in there. I've never noticed any rust spots though.

Every time I see these posts I feel like I need to do a better job looking for spots

 

Interesting. What part of the earth do you reside at?

 

The surface.

Seriously though, rust is my main concern with the 4runner - seems to be its achilles heel. I climb underneath to check on things periodically and looked really close when I had the panel cover off the back hatch rewiring a camera relocation kit. This is the first I've seen anything about inside the doors - not saying it's not a thing, just the first I've heard about it.

I don't even do an underbody spray, just try to wash road salt off as quickly as possible.

 

Also, are you sure it's from inside the door? I think I saw a thread recently where someone said the plastic trim on the door frame can dig into the paint and cause rusting.

 

This is what I saw
https://www.4runners.com/threads/door-sill-rust.11149/

 

You mean the door card/panel rubbing?

Door edge rust, at the bottom of the door is a thing. Sometimes it’s cause by the drain holes in the doors getting plugged from gunk, sometimes it’s poor QC from factory, or owners never wiping down the bottom part of the inside door and stuff just building up.

Living in the rust belt it’s common to spray inside the cavity to get stuff to creep down into the cavities where the door skins meet to prevent this occurring

 

Ahh, you're talking about the door itself, not the body underneath. I should probably take a closer look at mine. Out of site, out of mind.

I also don't live in the salt belt. Probably why ive never heard about that. Carry on

 

For the inside of doors, I've heard POR15 is the way to go. A friend of mine does this with great success.

 

Its a good thing to remove the door sills too, i did mine needed some minor touch up and did an undercoat (with woolwax) inside these rocker holes , im in eastern canada so rust exist here

 

Now there is a guy from my neck of the woods that knows what’s up! Yes, those sills will be coming off and I’m adding protective tape where they touch the paint and will shoot fluid film or rust inhibitor into that area too.

Any experience with RustCheck Rust Inhibitor?

 

Not with rustcheck but i used woolwax and fluid film a lot , my next step is to wire brush the welds on the frame and use a rust inhibitor then coat them

 

I took my 2013 doors apart last year for new speakers and Dynamat and have to say it was dry as a bone and 100% rust free. I think you should be fine unless it is a flood car.

 

Still going to shoot them.

I’m just undecided whether to do fluid film or rust inhibitor

 

Here's what I did:

Complete Corrosion Protection for my New T4R | Toyota 4Runner Forum [4Runners.com]

 

Fluid film is a rust inhibitor.

Regarding PoR15 inside the doors, that is some hard encapsulating paint. How do people even paint the inside of the door? And how is prep done? I would imagine it would require door disassembly. I would not want to hail mary the por15 into any cavity, because as an encapsulating paint, it probably relies on complete and continuous coverage.

Personally, I would stick to a rust inhibiting oil like woolwax, fluid film, etc. Just know, if you soray it up through the holes, the spray might travel to the weatherstripping for the window, and it will leave streaks or a line on the window as it goes up and down. For a long time lol.

I’m not super worried about door rust though, as long as you clean regularly. The body work is galvanized. It more the frame that’s susceptible to rust.

 

100% correct. POR15 is great stuff - if used in the correct application. Inside body auto body cavities is not a proper application. The beauty of oil-based products like Fluid Film, Krown, Wool Wax, etc. is that they do not harden like POR15. This allows them to seep into the smallest cavities and protect them from corrosion. This also makes them "self-healing" if they get scratched. You don't get that with POR15.

 

guess I meant do I go with Rust check ‘rust inhibitor’ or fluid film.

 

Make sure you don't plug up the drain holes or you will be creating a bigger problem. I tried spraying Fluid Film out of a can up through the drain holes and that had a tendency to plug up the holes.
Ended up spraying Hornady One Shot Extreme. Did that on my 2015 Chevy truck when new and no rust yet.

 

Yah I’d be worried about that, that’s why I’m
not doing POR15 in there, but you raise a good point about fluid film too. May do rust check spray instead it’s way more runny and would work better in this application.

 

So I sprayed RustCheck Rust Inhibitor inside the door cavity - the stuff is quite runny which I think is good and won’t clog the drains. I didn’t over do it either. But I forgot how much of a mess the little spray bomb adapter with hose and 360degree tip makes. Damn.

Pulled the door sill protectors, there was some rubbing off of those on the paint. So I had touch up paint and used that to cover those spots and then trimmed and installed 2” 3m scotchguard in the area to basically prevent the trim pieces from rubbing. Will see how well the clear film holds up it was my first time installing it.

Also used RustCheck Cost&Protect and basically sprayed inside the rocker through the mounting holes off the trim pieces with my extension and 360degree tip. Again, what a mess that wand makes.

So can someone tell me where exactly on the trunk/tailgate the trouble spots are? Is it behind that piece that says 4Runner? Is it the emblem? Like what concern and where is it on the rear end?

After I finish this, the next part is to remove spare tire, splash shields, wire brush areas and then take it in to get fluid film undercoated. Any paint in painting the frame after wire brushing?

 

I have a passenger door that has corrosion around the beaded seem where the sheet metal panels meet. The spots are small but if I left it unattended the door will rust out. All other doors, hood and rear cargo are clean and pristine. It appears to me to be a manufacturing defect. I found a few other cases on this forum where the corrosion really ate the door and Toyota covered it.

I have an appointment with Toyota under the 5 year corrosion warranty but I highly doubt they will approve a repair and I will have to fix myself or pay.

Truck is a 2019 with 49,000 miles.

 

Interesting. My passenger door is the same. All other doors pristine. my plan is to POR15 starter kit that part of the door and see if I can re-apply seam sealer.

 

What year is your truck?

 

‘16 Limited. This is what what it looked like prior to PO ‘fixing it’.

I’m ordering the por15 starter pack and going to wire wheel that, and apply the treatment. Only door that has any rust, all others speckles.

 

Strange its the passenger door only. The few cases I have seen on this site were the passenger door as well. I wonder how many trucks out there have this issue developing.

ACF50 is also a good corrosion killer and preventative that I have used in the past to spray inside cavities.

 

Ya no idea how this is but clearly it’s a manufacturing defect if others have it too. I applied RustCheck Rust Inhibitor - stuff is quite runny and still see drips and here, lol. Should do it,

The seam sealer is also gone so not sure if this is part of the cause but I should re-apply it when I repair.

 

Any chance the passenger door might have been repaired before you bought it? You'd be surprised how many new vehicles have paint repair work done that the dealer doesn't say anything about.

 

I looked at it very carefully and if they did then they one hell of a job. It looks wear/tear wise same as the others, hinges don’t look any newer etc.. if there are others out there with this door, no chances that all had passenger side door accidents to cause this