Undercoating, Rustoleum or not? Options

[HansJan]

Hey everyone,

While underneath the car (chasing an oil drip) I found that the undercoating has been wearing out.

In the front the oil drip (from cooler) has softened the undercoat and it basically fell of (like meat from Spareribs). I pealed it off completely and covered it with brown Rustoleum. The idea is to follow up with rubber undercoat type stuff.

Today I decided to remove the undercoat from the rest of the car (it had some worn out spots). It’s coming off very easily with a heatgun/sparula revealing a clean surface. It looks like the factory used a beige colored paint of some sorts.

Question for the group is. Should I brush the entire underside with Rustoleum or not?

Bonus question: what type (brand) of rubberized undercoat is best.

Car is a driver-quality six from 1970


I’m adding a random picture just so people will open the tread.

[East coaster]

I used this on my project: https://tcpglobal.com/collections/custom-co...cus-kit-bbl-2_2

[Dlee6205]

First and foremost, I never recommend any undercoat in an aerosol. I have yet to find one that performs well.

Second, if I simply touching up a car that still has some original undercoating, I typically use 3M Body Schutz Rubberized Coating. SEM also has a similar product that performs well.




If I want something better and am starting from scratch, like when I'm doing a restoration, I use a two part bed liner product.

[friethmiller]

I've used this on my last two builds with great results. Its like Schutz but paintable. Dynatron = 3M, I believe. I like to epoxy, seam-seal, undercoat, and then paint with the body color. I think the sixes where white with the body color partially sprayed-in from the sides. There's a PMB video where Eric explains this. This is back to factory type stuff and your driver-quality car can be whatever you want it to be. Plenty of good options listed above, as well. Good luck.

[dtmehall]

i had mine shot with POR 15

[HansJan]

Thank you all for the input.
Do I still start with Rustoleum primer or go straight to the undercoat products?

[dtmehall]

mine was preped with a zinc neutralizer

[JeffBowlsby]

Best quality product recommendation for a high texture, roll on application? Thinking about using 3/4 in knap roller?

[Ninja]

my survivor 75 has tan/beige undercoating with silver (body color) overspray.

The suggestions for Body Shultz/Dynatron are spot on.


Only way to go in my book. (IMG:style_emoticons/default/ninja.gif)

Another possibility is spray on bed liner material but there is absolutely no way I'd do that to a real -6.

Now, the POR15 is an un-penetrable paint. Bad to the bone...
It has a pretty good dose of super-glue in it.
Fatally dangerous fumes!

Super hard to get anything to stick to it. The company makes a primer for it that works OK but you have another expense/more work to make it look stock.

It CANNOT be exposed to sunlight. It will turn a "diseased" purple, looks terrible.

I've used it many times but once again, never on something historic.


Jeff, they make rollable bed liners, I've never used them.

My 75 914 will end up with bed liner on the bottom but my car is a BUB 1.8L and not nearly as valuable as a six.
I will also use POR15 on a few spots on the car.

[Geezer914]

I used brush on bed liner.

[dtmehall]

mine is a 73 1.7 driver. my goal was to rustproof the pan

it won't be painted, it will just be flat black

[Ninja]

i had mine shot with POR 15

mine is a 73 1.7 driver. my goal was to rustproof the pan

it won't be painted, it will just be flat black

That looks KICK ASS for a daily fun car!

Nothing will stick to the bottom of that car.

As long as you keep it shiny side up the sun will not be a problem.

I think it will still be nice 50 years from now...

If you want to change the look or do any welding, you will have to deal with the POR15.
Removing it usually requires grinding it off. (IMG:style_emoticons/default/headbang.gif)
It will laugh at mere sandpaper.

The draping in that picture looks like a DEATH TRAP to me.

I'd want a full-on paint booth style respiration system before getting in there with the fumes!

[dtmehall]

i had mine shot with POR 15

mine is a 73 1.7 driver. my goal was to rustproof the pan

it won't be painted, it will just be flat black

That looks KICK ASS for a daily fun car!

Nothing will stick to the bottom of that car.

As long as you keep it shiny side up the sun will not be a problem.

I think it will still be nice 50 years from now...

If you want to change the look or do any welding, you will have to deal with the POR15.
Removing it usually requires grinding it off. (IMG:style_emoticons/default/headbang.gif)
It will laugh at mere sandpaper.

The draping in that picture looks like a DEATH TRAP to me.

I'd want a full-on paint booth style respiration system before getting in there with the fumes!

the passenger compartment was de-rustified previously (not with POR 15), so I would think that the chances having to weld on the pan are low

[burton73]

WURTH brand is what I used on my 6 in Tan. They are not selling it in tan anymore.
My 1970 car came with tan back in the day. The can of underseal works well. I used it on my 74 car that is now Mark Sonners Blue car.I can find a picture if it but the BK works great.
Prep the metal so that it is clean.

Best Bob B

[930cabman]

as any applied paint/undercoat/..... it's all about the prep

If you can get a "near white" finish with a decent profile, there are a couple routes

The rest of us can get most of the rust gone and a reasonably clean dry surface. For this I use a corner hardware store oil based enamel. Benjamin Moore has a 1320 primer we have used and it seems ok. It's easily color matched and from what I can tell it's as good as any other

[Flyinlow]

Thank you all for the input.
Do I still start with Rustoleum primer or go straight to the undercoat products?

I used ppg 2k primer on a clean surface then raptor tintable bed liner seam sealer etc look forward to virtually indestructible coating

[bkrantz]

FLAPS undercoating spray is evil and should be banned. (IMG:style_emoticons/default/mad.gif)

[Ninja]

FLAPS undercoating spray is evil and should be banned. (IMG:style_emoticons/default/mad.gif)

Sounds like there is a story there!

Inquiring minds want to know...

[dtmehall]

(IMG:style_emoticons/default/popcorn[1].gif)

[bkrantz]

FLAPS undercoating spray is evil and should be banned. (IMG:style_emoticons/default/mad.gif)

Sounds like there is a story there!

Inquiring minds want to know...

My 914 project arrived with black "rubberized" undercoating on EVERYTHING. Inside the passenger compartment (trying to hide rust and cheap sheet metal patches), in the frunk (same, including up under the cowl), in the trunk (same), much of the engine compartment--pretty much everywhere but the actual bottom of the floor. and of course all the collateral damage from overspray: mechanisms, motors, connectors and of course the wiring harness. I probably spent an entire week of work time just cleaning the harness.

And I have dealt with similar undercoating crimes on other cars.