Working thru rust repair and refinish of my 2000xj underbody. Can't believe how many factory holes are in the frame rails. Understand necessity of drainage etc, but was wondering if it makes sense to close up some of the holes. Going to be using internal frame coating and may consider a fluid film or cavity wax in addition so would leave whatever holes are necessary to allowed access. I can still eliminate 4-6 holes on each side that are doing nothing but letting salt and brine in. Any comments are appreciated.
thanks

Personally I wouldn't.
As a matter of fact kinda wish there was a couple more holes so I could get in there better.
I used the Eastwood Internal Frame coating too.
There are guys though that have said that does more harm then good.
Oh well.
LOL.
I Fluid Film in there too. But I only Fluid Film for the winter.
Power wash (inside the uni-body too), dry, and Fluid Film in October. Power wash in April and spot here and there with Fluid Film.
I go to town with it. Too me it is not a less is more thing.
But working under the Jeep in the warmer months it can get messy which is why I don't reapply in April.
Couple things.
I have never really been able to determine where the rear diff breather goes from the white nipple on the outside of the uni-body that the hose attaches too.
I don't think it is right inside the uni-body there but didn't want to take the chance that it was.
Thinking covering it in frame coating and/or Fluid Film would not be a good thing.
So I extended my rear diff breather to the front so I could go to town back there too.
Just in case.
One thing I wished I did do before I used the internal frame coating.
Google cleaning inside of frame in TJ Jeep. I like the chain and cable idea with the drill.
Figured it would have cleaned it up some before using the internal frame coating.
Using spray cans or the gun kit for the Fluid Film?
The spray wand for the Fluid Film, and internal frame coating, kinda sucks IMO.
Cause of the curl in it.
I bough this to use with spray cans. I like that they are straight.


Didn't use it with internal frame coating, wish I knew about them when I did that, but do with the Fluid Film.
But you need to take the "cap" off the Fluid Film wand and put it on the 3M wand. Cause the cans for the Cavity wax are different.
But also too that 3M kit was so much cheaper when I bought it. Thinking $16.
Last tip.
Put some tape and inch or two from the nozzle on the wand.
So when pulling it out when you see the tape know to let off on the spray can.
Not a big deal with the Fluid Film but it is nice to not be spraying internal frame coating everywhere outside of the uni-body.
LOL.

I would leave them as is. They are 22 years old at this point, if they were going to cause an issue, they would have long ago. Look up Toyota Tacoma frame issues if you want to see what I mean.

I suspect closing up those access holes will just trap more moisture.
I agree with above, go nuts with the fluid film, I use gallon cans, not the sissy expensive rattle cans.
Where I live you are driving in salt and frack brine from Thanksgiving to Easter, fluid film does seem to work applied annually. It's messy and smells like wet sheep but it's better than rust.

I use gallons too cause I own a compressor and the gun kit.
Thinking at least a 1/2 gallon at a whack.
But my experience with 360 degree spray hose with the gun kit is that output is somewhat lacking.
Now with a spray can and the wand you can gunk up in there so much better.
Why I use spray cans for the uni-body and my running board rails.
My favorite part of Fluid Filming.
Watching the overspray burn off.
LOL.

From the factory...

https://truckworx.com/wp-content/upl...1-1024x768.jpg

You'll notice that there isn't one single hole on the top or bottom flanges; those are the important surfaces...