Rust proofing new W108 fenders.

[SickFinga]

I got new fenders fro my W108 and I was wondering if anyone got any tips how I should rust proof the inner parts? I'm looking for something that provides a lot of protections since W108s don't have fender liners and due to the design of the fender it has tons of nooks and crannies where all the dirt accumulates.

Does anyone know what Mercedes recommends?

[97 SL320]

Don't use spray can " Rubberized undercoating ". Sure it goes on looking great but it soon flakes off.

I'd clean the area well and use Rustoleum to get a good base. Rust usually starts at sharp edges so make sure they are covered.

I then use _rust proofing_ not _under coating_. Rust proofing is a thin waxy coating that skins over but does not dry where undercoating tends to dry out and crack leading to water being trapped.

Have a look at Rusfre 1000-1 Black and 1000-C Clear. https://raybuck.com/product-category/coatings-adhesives/undercoating/ Both are speced for inner panels but I've had good results with the black on exposed areas.

I'd have a look at making inner fenders. I frequently use polyethylene plastic from oval track suppliers to make rear inner fenders for pickup trucks and fill in front inner fenders. This comes in 24" ish wide rolls. https://www.speedwaymotors.com/Colored-Plastic-Rolls-10-Ft,1557.html

It forms well with a heat gun but be sure to heat a wide area and clamp things into position before it cools. I use small stainless screws and nuts to hold things together.

[TX76513]

I have used Bed Liner for new fender parts. Its self etching and holds on great even on painted/clear coated surfaces.

[Idle]

I would like to second everything 97 SL320 said. I deal with a lot of Fintails and Pontons. The Pontons seem to hold up better than the Fintails and the 114/115 and even the 108s from a rust standpoint.

The difference? The 'undercoating' dealers started pushing during the middle 60's. The spray on that cracks and traps water under the floors and trunk area.

Not all dealers did this. Some actually sold the customer on it before applying it. Others did it as a 'mandatory option' as they once called such profit packs.

I know at one time there were professional rust preventative treatments dealers sold that involved pumping a waxy substance into every part of the body that didn't show. But I can't remember the name. It was popular in areas of the country close to the sea where the salt air would eat up a car.

Anyone know if this company is still around? Auto makers going to a lot of galvanized body parts has put a big dent in that market.

[Bogfrog]

You could do what the old timers in New Hampshire did. Spray diesel fuel on the exposed parts and drive down a dusty dirt road.

[Mike D]

Use caution when using any of the "rust proofing" products.

The spray on stuff is fine if you use it for what it is made for. Sound deadening and rust protection for surfaces exposed to external contact with rocks, chemicals, etc.

It is NOT rust proofing to be sprayed willy-nilly beneath the car and can cause more harm than good.

The "Kiss of Death" for all old Mercedes!

I believe the wax based product is called "Waxoyl". If applied incorrectly it will cause the same problem as the Ziebart.

https://www.waxoyl-usa.com/

[if6was9]

Waxyol

https://www.waxoyl-usa.com

Fluid Film is another product that works well but is not as permanent as Waxyol, if you have easy acess like it sounds like you do with this 108 application it would be easy to renew the application every couple years or so.

Fluid film is more liquid and does not harden so to speak. It's lanolin, sheep sqeezins. it's somewhat more DIY friendly and less expensive but not as long lasting is the trade off.

https://www.fluid-film.com/