Opinions on this rust..

[mabbonizio]

Hi Folks,

I recently noticed that the rear left door seal of my 82 240D has a nice leak when it rains. Today i started poking around the floor board and found the pictured area rusted out.

Ideally I would like to wire brush this, coat it in POR15, then either fiberglass over it or glue fresh metal in (i'm not a welder)

Does anyone see anything wrong with this plan? It looks to me like the area is the floor pan and non-structural.

I've checked the surrounding areas (especially by that rear subframe mount) and the metal appears MUCH thicker there and does not appear to be rusted

[97 SL320]

What are the rules for safety inspection if they exist in your state?

Welding is always better however, sheet metal and steel pop rivets are a second solution that is much better than fiberglass because fiberglass will eventually crack off the steel as it flexes.

When using pop rivets, I use Clecos ( temporary rivets ) to hold the patch in place as I drill holes. The Clecos are removed and chips cleaned off. A bead of DAP Dynaflex 230 sealer is placed around the patch then rivets set. This sealer is found in most any home center and is the only stuff to buy as it stays flexible. This seals the patch from both sides.

As for gluing, there are structural adhesives for body repairs but they will be specifically labeled as such.

[mabbonizio]

Originally Posted by 97 SL320

What are the rules for safety inspection if they exist in your state?

Welding is always better however, sheet metal and steel pop rivets are a second solution that is much better than fiberglass because fiberglass will eventually crack off the steel as it flexes.

When using pop rivets, I use Clecos ( temporary rivets ) to hold the patch in place as I drill holes. The Clecos are removed and chips cleaned off. A bead of DAP Dynaflex 230 sealer is placed around the patch then rivets set. This sealer is found in most any home center and is the only stuff to buy as it stays flexible. This seals the patch from both sides.

As for gluing, there are structural adhesives for body repairs but they will be specifically labeled as such.

The car just passed inspection, however the undercoating had hidden this rust. Had I known it was there I would have asked the mechanic to weld in a patch as I had asked him to fill another patch

Would really like to patch this myself tho.

[kerry]

I don't see an issue with glassing it. Epoxy and S glass.

[barry12345]

Best option it was just an area where moisture accumulated. If not you really want to have a look around that car. That is really heavy scaly rust where the metal has returned to primarily just iron oxide. When it looks like this usually you will find it separated in areas throughout the metals thickness. It remains partially intact but very weak.

You are right in that the undercoating can hide things really well until they structurally cannot support it anymore. If I find rust like this and I live in a rust belt. I am going to carefully probe important areas. Hopefully this is just a localized issue. Yet for safeties sake you have to make sure.

As an example my neighbor had a ford station wagon. He dropped over with his car to use my shrinking/stretcher metal shaping equipment to manufacture a patch for his rear roof just above the rear door of the wagon.

He asked me how I would repair one of his rear shock towers. A quick check indicated he had no holes in the floor but it was totally compromised right from the back to the front. I could easily poke an awl through almost anywhere. So I told him since I was not involved in the metal repair. Scrap the car.

I had also put it up in the air and checked it before giving this opinion. He too is dead now as the years passed. Well before his demise. A car hit his with his wife driving. The car folded up really bad and killed her.

I think the amount of corrosion in that car was a major factor. The odd thing with that car is most the sheet metal topside was in decent looking condition. The roof metal failure just above the rear door I thought strange initially.

Possibly Ford used a lot of poor recycled metal in their floors and chassis structural components. I think if I remember it was a little ford escort wagon. I also saw a Vega station wagon we owned ourselves lose its floor in the same manner in those days.

Where am I going? Mercedes uses thick metal rocker panels for unibody support. The area you have an issue in should undergo a strong repair. If the rust is locallised. Structurally the area is signifigant.

[Mxfrank]

Rust through and open seams in a unibody car should always be treated as a structural problem. Weld it.

[Dan Stokes]

Originally Posted by Mxfrank

Rust through and open seams in a unibody car should always be treated as a structural problem. Weld it.

X2,000!

There is a lot more rust than you're seeing here and it IS a part of the structure. You can save a lot in the welding if you clear everything out of the way and clean off the metal back to clean virgin stuff. Then the welder can just fit and weld the patch so you don't have to pay to have the grunt work done.

Good luck!

Dan

[mabbonizio]

Originally Posted by barry12345

Best option it was just an area where moisture accumulated. If not you really want to have a look around that car. That is really heavy rust where the metal has returned to primarily just iron oxide.

You are right in that the undercoating can hide things really well until they structurally cannot support it anymore. If I find rust like this and I live in a rust belt. I am going to carefully probe important areas. Hopefully this is just a localized issue. Yet for safeties sake you have to make sure.

As an example my neighbor had a ford station wagon. He dropped over with his car to use my shrinking/stretcher metal shaping equipment to manufacture a patch for his rear roof just above the rear door of the wagon.

He asked me how I would repair one of his rear shock towers. A quick check indicated he had no holes in the floor but it was totally compromised right from the back to the front. I could easily poke an awl through almost anywhere. So I told him since I was not involved in the metal repair. Scrap the car.

I had also put it up in the air and checked it before giving this opinion. He too is dead now as the years passed. Well before his demise. A car hit his with his wife driving. The car folded up really bad and killed her.

I think the amount of corrosion in that car was a major factor. The odd thing with that car is most the sheet metal topside was in decent looking condition. The roof metal failure just above the rear door I thought strange initially.

Possibly Ford used a lot of poor recycled metal in their floors and chassis structural components. I think if I remember it was a little ford escort wagon. I also saw a Vega station wagon we owned ourselves lose its floor in the same manner in those days.

Where am I going? Mercedes uses thick metal rocker panels for unibody support. The area you have an issue in should undergo a strong repair. If the rust is locallised. Structurally the area is signifigant.

Hmm.. this car is relatively rust free as I have poked around extensively.. it appears that a good part of the rear window seal simply disintegrated and allowed water to pool right into the back of the floor plan where the rusted area is... Definitely leaning towards having my mechanic repair it if it is indeed a structural area.

[barry12345]

Originally Posted by mabbonizio

Hmm.. this car is relatively rust free as I have poked around extensively.. it appears that a good part of the rear window seal simply disintegrated and allowed water to pool right into the back of the floor plan where the rusted area is... Definitely leaning towards having my mechanic repair it if it is indeed a structural area.

Depends where you live but most repairs should include excluding oxygen from the bare area. Personally I like to heat up grease and spray it. Also remember we live in an area with substantial rust belt problems. I wait until I have done the repair and used paint on the external surface. Then drill holes or whatever to gain access for my long applicator nozzle. The grease slows down the existing rust rate to almost nothing and protects the new metal.

We still have a three thousand pound output hydraulic pressure pump that is designed to spray a grease and graphite mixture. We used to buy it in thirty gallon barrels and the unit sat on top. I no longer think the barrels of product are available.

[Simpler=Better]

$45 will get you a decent angle grinder, $20 for a decent cup brush.

Go to town stripping back to solid metal, if it's minor you can fix it yourself, if it's major you just helped do the prep for a pro.

[crazy4diesel]

Would totally fiberglass it. Grind all points where glass will cover metal first, fiberglass it on BOTH sides. The reseal with good undercoating. As to popping off, maybe in 10-15 years.

[HuskyMan]

If if were my car I'd take it to a body shop trained and certified in Mercedes Benz repair procedures. Let them put it on the lift and inspect all areas of the undercarriage carefully. Believe me, a second set of eyeballs can show up issues you have no idea exist. Tell the body shop you need a WRITTEN report detailing the problem/trouble areas.

[dude99]

You could also use POR15 and fibreglass cloth. Works like a hot damn.

[BillGrissom]

I don't see your photo. I wouldn't worry about structural issues if just an isolated rust-thru. Of course, undercoating hides much, so poke around. On other sites I have seen tremendous rust-thrus in convertibles yet the car is still magically held together somehow. A car with a full top is much more rigid.

[vtmbz]

Id hate to take a hit from the side in a car with paint and cloth floorboards. Unibodies rely on all their parts to be functional. Because youre not inside a frame, every piece of sheet metal does double duty. That being said, ive certainly careened around in a few rust buckets, and came to no harm. But I wouldn't do that in downtown Boston, for example, not these days of distracted drivers.