Undercoating an Already Rusty Undercarriage?

[William Pierson]

I spoke to my Hyundai dealer today and they told me I qualify for campaign TW9. The only information I could find was this:

https://testing-public.carmd.com/Tsb/Download/118814/5003643

I’ve got a 2010 Elantra Touring. My arms are pretty rusty. I’m not seeing much loss of mass, but they’re rusty. In the document, the only prep involves pounding with a hammer and then wire brushing. Perhaps a few hours of wire brushing might take off a portion of the rust, but, I really don’t see my dealer putting in that much time on a 9 year old car.

Is undercoating already rusty parts going to make my rust problem worse?

Is there anything I can do to prep for a better result? An undercarriage wash?

My appointment is for Wednesday, and I noticed that it’s going to rain tomorrow. I’m guessing that undercoating rusty AND damp parts is even more problematic, correct?

Do I trust my dealer to not make my rust worse or should I refuse the work?

Topic

[Dave Tidman]

Did you get a notice from Hyundai, and are they extending any warranties based on this TSB?

I would ask the dealer what specific prep work they do. Reading the tsb I didn’t see any specific rust removal prep work.

These are always difficult. In theory, cutting off the oxygen and moisture from the rusty area should stop the rust, but they need to be perfect to accomplish this.

Good luck, let us know how it goes.

[Richard Kirshy]

JMHO here …
prep involves pounding with a hammer and then wire brushing.
This will loosen exterior rust flaking, though I can not see them working to expose clean metal on the entire undercarriage.
As far as the internals of the under carriage …
Beating with a hammer will knock loose flaking rust, but you can forget about any wire brushing.

FYI..
If they are using some type of rubberized or asphalt rust proofing on the exterior undercarriage.
It is better than even money it will crack and/or separate allowing moisture between the undercoating and metal.

The vehicle is 9 -10 years old.
My suggestion, if you want it done as good as possible would be to do it yourself.
I would follow the basic outline the TSB suggests with a few changes.
Instead if beating the frame(s) with a hammer.
Invest in a inexpensive air hammer.
It will work better and save time.
Instead if a wire brush, try a assortment of wire wheels on a drill.
Again, it will work better and save time.
After removing and cleaning off as much rust as possible apply a rust converter to the bear metal both internally and externally.
Now as far as rust prevention…
For the internals of the undercarriage, I would suggest CRC Extreme duty Open Gear and Bar Chain Lube
This stuff sticks to metal, and remains ” soft ” , it does not dry out, split or crack.
And it wicks into all areas.

As for external rust proofing.
I use a mixture of boiled linseed oil, bar & chain oil and melted toilet bowl ring wax applied with a paint sprayer.

Keep in mind no matter what, rust proofing will need to be reapplied every year or two no matter if you have it done professionally or yourself.

[Author]

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