Ok got pans welded in just got a question about is it a good idea to also use seam sealer on the seam underneath vehicle? Seam seal it also or leave it unsealed so water won't get trapped? Funny in all the clips I've watched and the forums I've been too did not see anyone mention about the outside seam if the pans were overlapped some.Thanks

 

I had to do floor pan replacements on my MJ. I seam sealed both inside and outside then primed, painted, and then undercoated the new panels.

 

Yea thats what I was also thinking but figure I'd ask just in case since I don't recall anyone showing the bottom side as also being done. Hoping to finish it up and another week or two been working nonstop every weekend for about a month (well about 1030AM to 6:00 PM since any earlier / later its too dark. Just got done putting a 2nd coat of black bullet over most of pan got one more spot to weld and a seat bracket for drivers side to weld but ran out of gas. Going to eventually prime and paint with enamel paint.

 

I would seam seal inside and out. Water can splash "up" from the underside as well. I once had a car with a hole in the floor (small one). One time I drove through a puddle and one of my buddies in the back seat got the biggest spray on his legs. Hard to believe that much would have come through a small hole.

If your rig has a roof rack, you should take measures to make sure the holes around the mounting bolts are sealed. It's a major source of leaks inside. It doesn't have to be extreme, just a small trickle a couple times a week can add up to we carpets which really don't dry out underneath. And make sure there aren't any holes in the firewall too.

 

i replaced my pans this summer and also seam sealed on the outside.

 

Thanks all for the replies! Would it be best to use the brushable seam-sealer on the interior and use the urethane sealer on the exterior? Can the regular brushable seam sealer go over top of the urethane?

 

Well, if you wanted to do it 'correct' 3M makes a 2-part urethane seam sealer used by car companies and body shops. It's expensive but a great product. Then they also have an autobody seam sealer that comes in like a single-tube caulking tube. That's not too bad, but it does crack after many years. ...even though they say it doesn't. Same as the stuff that comes in a can. But the brushable autobody seam sealer stuff isn't too bad and it's easy to work with. It's somewhat costly though.

If it were me, I'd just get a $2.50 tube of latex caulk. I've done it and it works well. Not silicone caulk, Latex caulk. The reasons are: 1) it's cheap, 2) easy to spread and work with, 3) dries fairly quick, 4) takes (and holds) paint exceptionally well ..better than silicone or urethane. 5) doesn't crack

If painting isn't an issue, then a urethane exterior caulk from the home center is a fantastic product once cured. What I *wouldn't* use is silicone caulk.

 

I applied brushable seam sealer on the top and bottom sides. I masked off the seams and put it on over POR15 and it worked well. I finished it off with a gravel guard undercoating.

 

Thanks, I have both a can of brushable seamsealer in a can and a tube of the 3m urethane (not 2 part) was thinking maybe just use the urethane for the underneath stuff.

 

Looks good! How much seamsealer did it take? I have a can of the brushable and thinking I may need to get another.

 

To be honest I can't remember. I know I didn't use the full can for both floor boards and the cargo area floor. It was easy to apply and a little bit goes a long way. I found brush on sealer easier to use than a tube and caulking gun for what I had to do. Masking the area helped to keep things neat.

 

please guys use good seam sealer like the 3m stuff but do not waste your money on POR 15 that stuff is garbage ! use something like Sherwin Williams sea guard or axalta corlar 2.1 epoxy mastic to cover it up it will last forever !

 

That's funny … I've been using POR15 for 30 years or so. Never had a problem with it.

 

Yeah that!

We have been using it for a long time to, and NEVER a problem.
I had to fix most of the passenger side pan this last summer, and I used SEM seam sealer in a caulking gun tube.
Applied it to the bottom, and inside the cabin. Then I applied POR15 inside the cabin, and used Automotive paint on the underside, followed by Eastwood Rubberized undercoat.
For the one side I used just about one tube of SEM seam sealer.
Don't cheap out on the products you use.
Replacing panels is not worth doing again in a few years.

Also Don't use LATEX caulking.
Remember it is WATER soluble.
HINT HINT!
There is water in it till it dries.

Water and clean bare metal rusts. House caulking is meant for "Home repair", not automotive repair.
The reason behind using "seam sealer" in the first place is to keep water out of the seam.

 

So far I used POR-15 on the inside of the rails,2 coats of Black Bullet on the inside of the pans. Plan is to use some Rust-Oleum Stops Rust 32 oz. Rust Preventive Primer then Evercoat 365 seamsealer top off with Rust-Oleum Stops Rust 32 oz. flat black Protective Enamel Paint. Bottom will be same with last coat will be 3m rubber undercoating.I don't know if it will stick to enamel paint unless its scuffed up so may just omit the enemal paint on bottom....unless I find proof that it will.