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Undercoating?

Started by GSK11740, 23 September 2005, 01:44 PM

GSK11740

Hi! I'm new here. I have a '79 300SD I'm restoring and I have run into something I have never worked with before. What is this stuff Mercedes uses for undercoating and how do I get it off? I've read that it's best to remove it since it hides rust but I can't find any info on how to remove it. The undercoating used on american cars just scrapes off. It's messy but not that hard. This stuff seems indestructable! Help?

Mforcer

Hello and welcome to the forum.

Where did you read that it is best to remove the undercoating? I have never heard anything of the sort. The only thing that the undercoating may do is hide rust from view but it will not cause rust. Tackle the cause of the rust first.

Rust can be a problem when water pools inside the car from a leak. The floor carpets have a foam backing which absorbs water and the only way to dry them is leave them in the sun for a couple of weeks. Leaving them in the car while wet will cause rust in the floor of the car.

If you check under the floor carpets for water and signs of rust then you shouldn't need to worry about removing the undercoating.
Michael
1977 450SE [Brilliant Red]
2006 B200

GSK11740

Quote from: "450SE"Hello and welcome to the forum.

Where did you read that it is best to remove the undercoating? I have never heard anything of the sort. The only thing that the undercoating may do is hide rust from view but it will not cause rust. Tackle the cause of the rust first.

Rust can be a problem when water pools inside the car from a leak. The floor carpets have a foam backing which absorbs water and the only way to dry them is leave them in the sun for a couple of weeks. Leaving them in the car while wet will cause rust in the floor of the car.

If you check under the floor carpets for water and signs of rust then you shouldn't need to worry about removing the undercoating.

I can't remember where I read it. It's been a couple of different forums though. Don't worry. I'm not taking it all off. After trying to remove some of it, I've decided it's way too much work for me. I'm having enough trouble getting it running right. I want a nice driver, not a show car for Pebble Beach. I have had some rust pop through the undercoating in a couple of places though, such as around a couple of body seams. The floor is actually solid. The only real rust is along the rockers and the front fenders. For an east coast USA car, I got pretty lucky. Most of them around here are "swiss cheese".

Denis

Hi GSK11740

Dont bother removing any undercoating that is solidly attached but do cut out (chisel) any loose portions, use a wire brush and and treat with rust inhibitor (turns any rust into a black surface) then you may want to apply some undercoating (not thickly).

In France, we have a cheap aftermarket undercoating called Blackson and when our cars go for a technical check (like the MOT test in the UK),any "Blackson"ed surface results in a comment : cannot check metal as hidden from view (!) Enough said.

However, I have had success using an epoxy (naval) paint on a clean, de-rusted surface. The naval paint is impervious to water especially since it was designed for a much tougher environment.

Beware of rocker panel rust on W116, like all DBZ products of that era, the rust may be much more advanced than what you see. On a W116, you can remove the driver door plastic entry baseplate ? (it pulls out), fold back the carpet at the edge and see if the rust has started there. If not, it will be a simple rocker panel job. if the rust has perforated that area, do a complete inspection and act NOW. It can become a structural floor problem.


Good luck


Denis

GSK11740

Thanks Denis!

I have the car stripped down to almost a bare shell on jackstands (interior gutted, panels and glass removed, etc). I decided to take everyone's advice and not try to remove all the undercoating. So far, it's looking good. I do have some rust on the rockers but it hasn't come through to the interior. The floor is solid. Also when I pulled the front and rear windows, I was pleased to find it wasn't rusted out there either (everyone said it would be). I also checked around the front suspension mounting areas. Solid. I do have one spot where it rusted through right next to the fusebox that looks like it's going to be tough to get at. I guess I can thank 12 years of sitting under a tree for that one. The area was full of leaves and other crud. When I cleaned it out, there was the hole.

All in all though, I think I lucked out.

alabbasi

Take the pads under the carpet off, you should see the state of the floor that way.
With best regards

Al
Dallas, TX USA.

GSK11740

Quote from: alabbasi on 26 January 2006, 08:31 PM
Take the pads under the carpet off, you should see the state of the floor that way.

Those were one of the first things I removed (the smell of mold and mildew was almost lethal). The floor is mostly solid. Just a little bit of surface rust under the mats and one small hole under the parking brake pedal. I have 2 more small holes in the oddest places. One is next to the fusebox, through the firewall, another is on the passenger side firewall, behind the climate control servo. The floor is an easy fix but the two in the firewall are going to be tough to get to.

I really need to get that website up and the pictures posted so you can see what I've got to work with.

oscar

Hi all,

2 naive questions-

Is the undercoating your talking about the dimpled protective spray putty or whatever applied to the underside of the car?

Secondly, what part of the car is the rocker panel?

End naive questions.
1973 350SE, my first & fave

GSK11740

Quote from: mb350 on 27 January 2006, 08:16 AM
Hi all,

2 naive questions-

Is the undercoating your talking about the dimpled protective spray putty or whatever applied to the underside of the car?

Secondly, what part of the car is the rocker panel?

End naive questions.

You are right on the undercoating. The rocker panels are the curved pieces of metal that run under the doors and fenders on both sides (for a lack of a better description).

OzBenzHead

Quote from: mb350 on 27 January 2006, 08:16 AM... what part of the car is the rocker panel?

What Aussies might call the "outer sills" (compared with the "upper sills" or "sill treads", and the "inner sills", "side rails", or "chassis beams").

oscar

I call 'em "the black bits underneath".  :D
1973 350SE, my first & fave

GSK11740

Here's one I've heard before but am not sure of. What are "wings"? Is that the same as what we in the US call "fenders"?

OzBenzHead

Quote from: GSK11740 on 27 January 2006, 06:54 PM
Here's one I've heard before but am not sure of. What are "wings"? Is that the same as what we in the US call "fenders"?

US: Fenders
UK: Wings
Oz: Mudguards

oscar

#13
"wings" isn't that another loose term for "spoilers"?  That's what my wife calls 'em

Regarding the undercoating, is it just spray putty? Can you get it coloured or can it be painted and what with?

Also re: rocker panels etc,etc,etc.  I Did a search and found lots of sites pertaining to chromed or stainless steel panels.  Couldn't find 116 ones not surprisingly.  How do you think they'd look?  I'll have to try a photoshopped one.

1973 350SE, my first & fave

OzBenzHead

Quote from: mb350 on 27 January 2006, 08:05 PM
"wings" isn't that another loose term for "spoilers"?

That is a more recent usage of the term, but "wings" have always been the Britush term for (Oz) mudguards or (US) fenders.

There are spoilers and spoilers: there are the subtle ones that probably improve roadholding, and there are the outsized ones that are probably merely small-willy substitutes.   ;D