Post-Paint Undercoating Ideas

After the paint is done and while the cab is still stripped I was wondering what you guys thought about these items in regards to undercoating.
Goal being rust prevention.

1. Inside the door bottoms. Stick something like putty knives or wood shims up the drain holes, spray the undercoating along the door bottom on the inside and then pull out the spacers while still wet.

2. Cab corners. Do these rust out from inside or outside the cab? If inside, spray undercoating in the corners.

3. Door sill trough/channel. Tape off and spray inside the trough.

4. Inside the fenders anywhere?


Any other places that would be good to hit with undercoating?
Cowl was already done in body color undercoating.

I'm not a big fan of undercoating.

Inside the doors I'd rather spray something like that rustoleum leak stopper stuff.
This will make a complete bladder and bond better than anything short of professional bedliner.

In the cab you could do front to back from the downslope of the floor pan.
Having the pinch weld used for the door gasket means any slush or whatever just sits there.

A good idea is to get rid of any of that absorbent jute padding.
That stuff holds water like a sponge and starts to fester.
Some kind of closed cell foam like ensolite or even an old yoga mat is much better.

Fenders rot in the front back corners and above the rear wheels.
Spray up behind the plastic wheel liners, and consider drilling some big holes in the rear metal fender arch support.
Then water and muck have a way out, and you can flush it with a hose.

That's all I've got.

Make sure your cowl drains are open and free of muck.

I'm going to delete the rubber spouts entirely.
There shouldn't be any debris stuck in there without them

Thanks.
I have always been hesitant on the undercoating also due to the inability to see behind it so I'll check out the rustoleum product. Edit: just did and is it the same as flex seal aerosol? I used that in my 80's cowl as a quick fix and liked how it flowed out.

I wondered about the real benefit of those duck bills. If they are just for mice (?) then I'd rather take my chance with the mice.

I was going to go with the mass backing on the carpet. My thought process was that:

1. Would provide some of the benefits for heat/sound
2. Wouldn't be adhered to the floor so I could check under it/easily remove if necessary
3. Would provide a barrier between the jute and the floor pan so moisture would have to evaporate up and not soak down

"Fenders rot in the front back corners and above the rear wheels.
Spray up behind the plastic wheel liners, and consider drilling some big holes in the rear metal fender arch support. "

My fenders are at the paint shop right now - you don't happen to have anything showing what you mean for these, do you?

1. Front back corners
2. Behind plastic wheel liners
3. Drilling hold in rear metal fender arch support

Are all three of those regarding the front fenders?

Yeah, it's the same as Flexseal.
Comes in black, white, clear, and the elusive silver...

If a rodent wants to get in, it WILL get in.
Anyone who has been through a New England winter will tell you that.
The best defense is to not let your truck sit too long.
No one likes the smell of mouse urine wafting out of their vents, but at least you know it's time to smoke them out.

I have a lot of foil insulation and super sticky mass damping stuff from a studio I built for a drummer in my cab.
More on the passenger side because my ex would complain of the heat under her feet (and 460's create a lot of heat)
Then some white -batting-like mat. At least it's polyester and can't rot or support mold, fungus, etc...

I really meant, 'spray' as in rinse with the hose.
Due to my current lack of more 'normal' accommodations, my truck gets a bath -at best- 2 or 3 times a year.
When I do have a chance I will always wash underneath first.

One and two are in the front.
Three is in the rear, up on top, exactly where you see bed sides rot out all the time.

Ill see if I can get some pics when it gets light out.

Remember, I'm only one person on the internet.
My methods are mine. And I have to live with the results of my choices.
I can tell you what works for me, but what you do is yours to own.

ArdWrknTrk wrote

Remember, I'm only one person on the internet.
My methods are mine. And I have to live with the results of my choices.
I can tell you what works for me, but what you do is yours to own.

Oh no worries :)
I just like getting as many opinions as possible and then weigh them all out. Mainly to make sure what sounds like a good idea in my head doesn't have some flaw that I have overlooked.
I won't be hunting you down if I do something you recommend and my life all of the sudden plays out like an old country song.

And what's the fun in owning one of these if you don't have to fix/redo/rinse/repeat something on it all the time?

I tell Gary that an oil leak is free waterproofing.  
That people up here in the salt belt will spray the underside with bar & chain oil.

He says how nasty an oily undercarriage is.
Better than no undercarriage, I suppose.
Thing is, thick clingy oil (tackiified) will creep into cracks and crevices, and once there prevent water from collecting, or oxygen from reaching the surface.
This (electrolytic) process it what causes iron and the most noble -carbon- from reverting to their natural states: iron oxide and carbon dioxide.

Darren, that guy Mustie1 on YouTube melts toilet rings (beeswax) into bar oil and sprays it into pockets and crevices.
Not really the entire undercarriage.
It's an interesting concept, and it seems to work...

Major rot repair is never any fun.    

Wait a minute...... Cory's the only one who's supposed to be up with me.  
He's an hour east...  

This is just one spot where I cut away the rear inner fender when I put new arches on.

Another one forward, and on the other side I used a big step drill.
(cheap, from horrid fate)

ArdWrknTrk wrote

Wait a minute...... Cory's the only one who's supposed to be up with me.  
He's an hour east...  

I'm late today...mainly because I slept-in until 5:15am (Atlantic time) and then had to hook up my trailer to bring to work with me so that I can get somebody to weld a fender back on for me. I didn't have my normal coffee time at the computer this morning.

Anyway...

I'm a big fan of rustproofing spray...it is pretty much a necessity here if you want anything to last. I usually get our cars done annually, and I plan on having part of my truck done when it the painting is all finished (I'm dropping off the stripped cab/chassis next week).

The rustproofing shops here even have body colored plugs they use now which aren't as obvious as just plain black.

Now, there are two schools of thought on rustproofing around here. Some people prefer (and promote) the thick gooey stuff that you spray on and it pretty much stays where you put it. Then there are the guys that like the runny stuff that drips and creeps into every crack and crevice. The downside to the runny stuff is that it makes a mess...and of course it drips.

I like the runny stuff myself. On my Bullnose, I'm going to be pretty selective on where I rustproof it...it is not a daily driver, and it likely won't get driven very often in any kind of bad weather, and certainly not in the winter.

I'll be spraying the inside of the front fenders, the inside of the doors and cab corners, the underside of the cab, and the inside of the frame C-channel. I'll also do inside the tailgate (need to drill a couple hidden holes), and I'll spray the front and rear sills of the bed. I already rustproofed the areas where the wood is sitting...I did this just before I sat the wooden floor into place.

I'm waiting until the whole truck is finished...likely in a couple weeks time, and I'll get the spraying done and then leave it outside for a few sunny days to let it drip.

You're missing all the fun!!!  

Check out that guy Mustie1.
He sprays it on hot, with a shutz gun.

When it cools the wax stiffens up.
But it does flow into all the books and crannies.

Very true! Meant that more generally than to this specific case - absolutely wanting to prevent rust for as long as possible since this will be a daily driver in all weather.

Trouble getting to sleep last night and even more trouble getting up today after the 3 hours I did get :)

Will you be able to get to the insides of the front fenders after assembly?

This runny stuff - when used inside the front fenders and inside the doors is it a 'permanent' coating? I can see getting the underside of the cab and the frame getting done annually but wouldn't want to have to pull the door panels yearly.

kramttocs wrote

Will you be able to get to the insides of the front fenders after assembly?

Yes, fenders are no problem. They're more or less open on the inside anyway. Normally just spray in the upper holes and let the stuff run down the inside.

kramttocs wrote

This runny stuff - when used inside the front fenders and inside the doors is it a 'permanent' coating? I can see getting the underside of the cab and the frame getting done annually but wouldn't want to have to pull the door panels yearly.

Yes, it is permanent in some areas, but we have it done annually for our cars since they're driven in the winter on heavily salted roads, and it does wash off after a while. The door panels aren't pulled, they actually drill holes in the ends of the doors and use long wands to spray inside, and then use little rubber plugs in the holes. This is especially good for things that are usually enclosed, like rocker panels and quarter panels, "dog legs", tailgates, etc.

The key thing is getting the stuff in the right places, like into the seams and folds in the sheet metal, and behind fender lips, etc. This is why I prefer the runny stuff, but the down side is that it is messy, and you do have to drill holes in your vehicle which some people are very strongly opposed to, and I get that.

Oh, here...if you watch the video on their home page, you can actually see how they spray inside the doors.

https://www.krown.com/en/

Now that's neat (and a well done video). The holes in the doors make a lot of sense as does it being runny enough to flow down the front fender cavities.

Just got back from the paint shop dropping off my trim pieces and talked to the painter about this. Not surprisingly, he knew exactly what I was asking about and pulled out a can/wand of the 3M Cavity Wax that he likes to use.

So that takes care of the fenders and doors. I'll take care of the sill plate thresholds and inside cab corners once it is back in my possession.

Thanks a lot guys!

kramttocs wrote

Now that's neat (and a well done video). The holes in the doors make a lot of sense as does it being runny enough to flow down the front fender cavities.

Yup, and they do the same thing with tailgates. Drill a hole in the ends, and then run the wand back and forth through a few times to coat the inside. It's no big deal and you can't see the plugs with the gate closed anyway. It drips out the drains, but it does leave a nice film behind. It's funny...but after a while the drips stop, but then when the vehicle is sitting out in the hot sun, it will start to drip again...so it really is a commitment once you start doing this...lol.

Glad the body guy is good with rustproofing. It really is important that the product (whatever it may be) get into the right places. A door, or a tailgate for that matter, is never going to rust from the middle out...they start at the edges and around openings where the seams are.

It's a big enough business here that there are shops that only do rustproofing, and nothing else. Then there are lots of places that offer it up as an extra.

In any case, good luck with it!

This is interesting! Obviously not in a rust belt, but my truck has some rust on it in areas.

A mechanic friend said it must have spent some time on the coast, which I agree with, the truck was a RV hauler in it’s early years.

I’ve use corrosion inhibitors on this truck when I’m working on it, before putting it back together and such.

I’ve been using Amsoil HD Metal Protector and now Liquid Wrench Rust Inhibitor. Thinking of spraying the underside down with some.

https://www.amsoil.com/shop/by-product/other-products/cleaners-and-protectants/heavy-duty-metal-protector/

https://www.liquidwrench.com/product/rust-inhibitor/

A week or so ago I was looking over 3M on Youtube and came across a hour+ video on Corrosion Protection on newer cars & trucks after they have been repaired, it was an eye opener!
This is not the one I watched but I am sure it talks of the same stuff from just the 2 min. I had seen of it.
https://www.youtube.com/watch?v=eceOg7ifmIs
In short you want to use the3M cavity wax with wand, this stuff creeps every where.
It looked to be close to the stuff Eastwood's internal frame coating with wand.

BTW you guys talk of the fenders, cab corners, above the wheels on the bed to name a few areas DO NOT forget the roof along the rain gutters and A pillars!

I am not a fan of under coat. When dry it has pin holes where water and dirt get in and start rusting. Before you know it you peel off the under coat and you have nothing left of the metal.
You would be better off not using under coat so it is open to the air so it will dry.
Dave ----