I think I am losing my "floor"
 

Pete got an oil change today and since the whole flex disk disaster I took the opportunity to poke around the underside of the car.

Under the car, on the driver's side, close to the edge, right next to some triangular things held on with bolts, some rust has eaten through the metal whatever part that is. It is this black gummy stuff that I suppose is undercoating of some sort.

Given these circumstances, what should one do? Is the structural integrity compromised? is this a job for a welder? any opinions are appreciated. thanks

Jen.

Plenty of reading here.

http://www.peachparts.com/shopforum/bodywork-repair-paint-tools-tips-tricks/86054-who-has-most-rust-still-drives.html?highlight=Rust

It is a common problem.

Louis.

There was a lot of reading there...
but there are some threads which have really explored the practical things from small....to replacing the floor completely....
somewhere in the searchable archives....

I had an 85 300D with around 475k miles on it. The thing ran like a german clock but it was rusty as hell.

The rear floors had holes in them from water entering the cabin. The passenger rear seat bolt was gone. The fronts were starting to get holes.

I wound up making make-shift floor pans for it out of galvanized steel, and rivetting it down. I cut out alot of rusty metal and primed the area. Siliconed everything down. I also had a new seat mount as well as a seatbelt mount for the passenger side.. if anyone wants to see my handywork I can dig up some pics.

Jen-

I have that problem on my 240D and looks like I have it on my "new" W116 300SD. MBZ did a great job of undercoating the underside of the floor pan with a very durable rubberized coating. On the inside, they did a good job of noise proofing the cabin with some sort of spongy asphalt-like material. Sandwiched in between these two is your steel floor. The undercoating originally did a good job of protecting the underside of the steel from water splashing up from below. But when water gets past the undercoating through cracks, the water sits against the steel and rusts. Similarly, when water gets in the cabin from leaky windshields, etc, it gets into the spongy asphalt sound deadening material and rots the steel.

On my W123, even though both surfaces looked OK from the outside, when I pushed down on the floor I could hear a "crunch" like corn flakes in there. I peeled back the inside asphalt and found a hole about the size of my fist below the clutch pedal. I also found two more much smaller holes further back at the back of the front seat where the floor pan is welded to the rocker panel. After I ground all the rust away to white metal ,I patched the bigger hole with steel using a two-part epoxy metal bond that is used in the trade to glue on quarter panels. The repair has held up just fine for over a year. You may have to do something like this. You may also get someone to weld in new metal, or use fiberglass if the hole isn't too big.

But the most important thing is, you need to peel back any compromised undercoating or sound deadening material and see how extensive the problem is to determine the cause and corrective action.

Rick

OK. After reading your responses, it's clear that fixing this rust problem requires skill well beyond adjusting the valves. I mean you guys are talking about welding and riveting.

So let's assume that there are fist-sized rust holes on the floor. Is the car unsafe now? I thought i had a relatively rust free car. This really pisses me off.

So who fixes these things? a body shop guy? maaco?

Jennifer,
It is probably not unsafe. Ask around and try to get a good reference for a body shop that comes highly recommended. Take the car to them and get an estimate. I imagine though, that if you had the tools, you could do this type work seeing as how you have a background like you do (using your hands).
Jim

Jen-

If its just fist-sized holes, probably not unsafe. The car's certainly not going to break in half- but if you do a tango someday with an SUV all bets are off. The floor does tie things together nicely in the event of a serious crash. This is not something that should be put off for very long.

Except for welding, this isn't rocket science. I would at least dig back all surfaces until you get to solid metal and see what you (or they) have left to work with. Like many types of bodywork, doing a good job has a lot to do with how much time is spent. "Professionals" don't like to spend their time on this- they just want you to spend your money. Look throgh the archieves for ideas on how to fix this using things like phosphoric acid and POR-15 paint. You can't be sure a professional will take the time or use the best materials unless you watch him. Like doctors, this is an area where pro can bury their mistakes.

Rick

Riveting definitely is not rocket science. You can learn to do this. I suggest practicing with some scrap sheet metal (empty tin cans) and a pop rivet kit.

RUST thread
 

:D Yes; please, add them to this RUST thread. :D http://www.peachparts.com/shopforum/bodywork-repair-paint-tools-tips-tricks/86054-who-has-most-rust-still-drives.html?highlight=rust

POP rivets
 

If you can safely use a set of vise grips, you can use a pop rivet gun.... Less than $15.00 at any Wally World (Wal Mart). Spend a little extra and get stainless steel rivets, aluminum won't rust, but not very strong. Rivets and gun will be less than $20.00!! :D

Pop rivets are not structural. A rivet job is a bandaid patch, not a repair, something to get you home so you can repair it. Get them toes under the table.

The floor and roof of a unibody car are major load carrying structures. You do not want to compromise the structure of your car, your safety is at risk.

Rust is like the tip of the iceberg model. If you see a little you can bet there is more in there somewhere. Not always though, you may have one leak that makes water sit in one place and rust your floor. Battery acid may spill and rot your firewall. Etc, etc.

When you make a repair make sure that you are welding to structurally sound metal.

MIG welding is really easy to learn and you can probably find someone with a welder sitting around doing nothing that you can use. Set the heat and choose the wire size by the metal thickness. Set the wire speed by the sound. It sounds like sizzling bacon or such.

Welding is all about making puddles. If you are joining two pieces of metal you make three puddles, your welding wire makes a puddle and two pieces of metal make two more puddles. When you turn the three puddles into one puddle you have a good weld. Look for heat blueing on the backside of the weld to check for adequate penetration. Now you know what many people never learn after years of instruction.

Rust belt people get so used to rust they get numb to it. We only hope that thier numbness does not eventually lead to much pain and suffering.

Hope Pete is well again soon.

"Pop rivets are not structural. "
TRUE for the most part....

"A rivet job is a bandaid patch, not a repair, something to get you home so you can repair it."

Not true if done correctly.... just ask Boeing etc... entire planes are held together with rivets...

And most structural parts of FRAMES on old cars had rivets... Spring perches, transmission supports, the upper and lower A Frame mounts , etc.
All done with steel rivets.... typically 3/8ths thick stem.... and applied hot...

For rivets to be proper structurally one must do some studying ... for instance the relationship between the thickness of the sheet metal compared to the stem size of the rivet...and how close the rivets need to be placed.

The Eastwood Company catalog is great information ... there are spot riveting welders which only have to be on one side of the metal... as compared to the old days... and Aircraft tool supply is great reference....

http://www.aircraft-tool.com/

Leathermang is correct!!!
 

Rivets DO hold airplanes together!!! :eek:

I wouldn't trust a pop rivited floor pan to hold my seat in place during an accident. Point of note, NEVER use aluminum pop rivits on steel or vice versa, there is a thing called galvonic action. the dissimular metals will corrode even without water.