Opinion on Rubber Undercoat? - PeachParts Mercedes-Benz Forum

Strife · #1 04-03-2008, 12:55 AM

I redid my 380SL "daily driver" and I have tremendous fear of rust, having seen several of my cars get eaten alive up North. I like to drive, and I have another SL to drive in the summer only. This is the present state of the car:

1. All drains open (I actually check once in a while)
2. Rust in lower RH fender towards the door due to improper seal repair after PO collision - I repaired this and am satisfied that it is is now sealed and eliminated
3. Rust in lower front fenders (minor - eliminated)
3. A small amount of rust in the LH rear panel under the bumper (a bolt on, fairly inexpensive part, I might repair or replace)
4. 99% of the OEM undercoating seems intact except in the front of the front fenders and the metal piece that joins them in the front of the car under the bumper

I tried out this rubber undercoating spray and it seems to be a good idea. I've looked into "waxoyl" type rust preventatives. Any opinions of either of these, good or bad? It does snow a little here in winter, and they salt aggressively. However, I wash aggressively. I washed a car in 35 degrees/sunshine this winter!

compress ignite · #2 04-03-2008, 02:41 AM

Rubberized undercoating works,with ONE Caveat.
The under-body Must be Very,Very,Very Clean...Dry...and Absolutely Rust Free!
Otherwise you're just sealing up the INFECTION and IT WILL GROW!

Waxoyl is I believe the original Old Timey Sealant used in the spaces
you cannot access except with a narrow wand.(Pre 1950s).No one
has come up with a better formulation.The Waxoyl also has a rust
preventative.

alamostation · #3 04-03-2008, 07:17 AM

In states that have very thorough inspections, such as Iowa, where you get rejected for any rust-through, rubber sealant is great.

Years ago, I had a Sunbeam Alpine that I bought in Michigan. The body had been Bondo-ed to where it looked pretty good, but there was a big rust hole in the passenger's floorboard. It failed inspection.

I took the cardboard from a notebook, put it under the carpet over the hole and sprayed the Hell out of it with rubber sealant. It passed inspection twice before the car was sold.

I'm of the theory that if you spray the sealant on after a couple of hot dry days, or use a hair dryer on the rust, you are not "sealing up the infection so that it will grow". If water, salt and oxygen can not get to it, how will it grow?

Dee8go · #4 04-03-2008, 09:03 AM

Quote:

Originally Posted by compress ignite

Rubberized undercoating works,with ONE Caveat.
The under-body Must be Very,Very,Very Clean...Dry...and Absolutely Rust Free!
Otherwise you're just sealing up the INFECTION and IT WILL GROW!

Waxoyl is I believe the original Old Timey Sealant used in the spaces
you cannot access except with a narrow wand.(Pre 1950s).No one
has come up with a better formulation.The Waxoyl also has a rust
preventative.

Are you implying that the Waxoyl will work even if there is still some rust when it is applied?

compress ignite · #5 04-03-2008, 10:12 PM

Dee8Go,

The only Sane rust repair is to remove the rust,properly prep and treat the
"New" bare metal (Books on the subject of what is and is not "Treatment")
'Depending on the composition of the metal being treated;the wise Tech
uses only "Tried and True" methodology and chemicals.

Don't we all wish (to find the Holy Grail of rust preventatives)!

It does a better job in enclosed spaces (frame tubes,Etc.).

Lexxani · #6 04-04-2008, 08:03 AM

if you have a few minor spots of ruber undercote to touch up (in my case I ran over fresh painted white lines on the highway) I got a can of the rubberized tool grip stuff and a disposable paint brush, it did the trick excellent and matched perfectly. Be careful not to use too much as it will run and you will get little driplets on the bottom of the roll pan. As the others said, you MUST cure all rust first otherwise it'll grow. . .

Dee8go · #7 04-04-2008, 09:37 AM

Hmmm, so, you're saying the easiest way is NOT the best way to take care of rust?

I was afraid of that.

slavrenz · #8 05-13-2008, 12:34 PM

"In states that have very thorough inspections, such as Iowa, where you get rejected for any rust-through, rubber sealant is great."

Just exactly what kind of inspections are you talking about in Iowa? I live in Cedar Rapids, and have sold 3 vehicles, all of which had rust underneath, and was never "rejected" by a dealership.

Dee8go · #9 05-13-2008, 03:24 PM

I never heard of this before in Virginia, either. The floor in my SEC seems to be rusted through in places that are covered up by the under coating. It didn't fail because of it, but the guy doing the inspection told me it could fail in the future if I don't get it fixed.

JHZR2 · #10 01-03-2011, 10:35 PM

So what about if you are trying to start a regimen of something like waxoyl, krown, eastwood HD anti-rust or similar stuff? On a new car, let alone a 30 yo car, it is nearly impossible to be totally perfectly clean at least. Dry maybe, but clean? Inside of crevices? Likely not.

How critical is that? Shouldnt the product, if it has enough thin carrier oil/solvent impregnate any dirt? Id think it may even displace moisture.

Rubber spray undercoating may be another story, since it could possibly be porous to the weather and create a (tortuous) path for moisture to wick in and stay.

The OE coatings seem to do well when applied to clean metal, other than the gaps/seams, etc. At those points it would be nice to be able to seal or touch up, but if trapping dirt in does more harm than good, at some point, when you see a gap in the protective coating it is almost time to condemn, as you cant get it perfect.

How serious must one be, and does it differ by product?

compress ignite · #11 01-04-2011, 10:39 AM

"Water Always Wins"

"Rust Never Sleeps"

JHZR2 · #12 01-04-2011, 10:59 AM

Well that's all well and good, but we can at least try to protect as best as possible...

JB3 · #13 01-04-2011, 01:19 PM

I went and had my car sealed this year with some rustcheck stuff, similar to waxoyl in its performance. So far I have been very pleased, eventually the stuff washes off after about 1.5 years said the guy with regular washings and time, but is less likely to gum up drains, and done as yearly preventative maintenance religiously, certainly seems to me to be a great anti rust thing to mark off on the checklist.

I will continue to do it since I routinely take my car skiing all year, and also wash it regularly. I figure whats an extra 100 bucks a year if it actually does some good. Rubber undercoating is to me something that is the last layer put on after paint and actual rust repair has been performed.

JHZR2 · #14 01-04-2011, 01:52 PM

I had my Saab Krowned this summer which was good. I can take my other cars for waxoyl, as LI NY is closer than Ontario.

But all these things are internal Protectants. IMO the rubber sprays are not the same as the OE undercoat, and the sprays may offer highly tortuous but slightly porous coating which could set the conditions for rust... Unless it is sealed with a self healing waxy or oily coating, which may then not be compatible with the OE coating.

Lots to think about... Would love to do some tests on scrap samples of the OE undercoating for compatibility...