Author Topic: Box Section Rust  (Read 9580 times)

ptomey

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Box Section Rust
« on: August 03, 2007, 21:01:26 »
I’m entering my 3rd month of ownership and up to this point have done a lot of poking around for rust, which I keep expecting to find but haven’t yet (nothing serious anyway). Even having the entire interior & carpets stripped out revealed nothing but solid metal. The interior is pretty much back together and while messing around in the engine compartment I found it. Rust in what I thought at first was a bizarre place until I searched the forum and found that it’s more common than I would have believed.

 
quote:
Quote from an earlier post by George Davis 1/17/07

It's also possible that the box-section stiffener in the front fenders is bad. It's inside the fender on the engine bay side and can be seen by looking in and up; it runs from the headlight bucket to the firewall. The flat top rots, because that's where crud and salt collect. You can't see the top, you have to feel it; but wear gloves, because if it is rusty you'll shred your fingers. The book method for replacing this stiffener involves removing the fenders, because there is no way to access the top to weld a new one in place. Removing the fenders is another major surgery. But a new stiffener can be installed by splitting it lengthwise, welding the upper section in place from below (inside the stiffener), then welding the lower section in, and then welding the two sections together along the split.


The area which I believe is referred to as the “box section” or “box section stiffener” (please see the area labeled in the photo and start by telling me the correct name for the area I’m describing). It’s the area where the front fender meets up with the inner fender as seen from the engine compartment (where the shock tower mounts are).



The rust itself cannot be seen in the picture since it’s all underneath the lip so I’ll describe it. Both the left and right side are afflicted similarly. Some areas totally clean, spot welds in perfect shape, further down the line some surface rust. In a few spots, holes where the metal is rusted away, sizes of holes ranging from 1/4” x 2” to as large as 3/8” x 18”.

I’d like to discuss an intermediate term solution and a long term, permanent solution. For the intermediate term, is it feasible to clean up the rust with a wire brush and other tools to eliminate the remaining rust and then paint it with some sort of rust converter? I plan to detail the engine compartment within the next few months including removal of the engine so that I can paint the engine bay Light Ivory, same as the body. (As you can see it’s currently painted flat black). Should I be concerned about the missing metal for structural reasons? As long as I can halt the rust from spreading, the way I use the car would preclude water and dirt re-entering the area and starting the process over.

Next for the permanent solution, Welding in patch metal seams like the answer although it’s pretty tight in there and I’m not sure it could be done without a LOT of body disassembly.

Finally, I’ve heard mention of a rubber gasket related to this area. See quote:


 
quote:
Quoted from an earlier post by Jeff C. 11/17/05

I've been busy replacing driver side firewall, floor pan and side rail. As I reassembled the car I noticed what I believe is a likely place for a failure in the weather tight seal between the firewall, side rail and inner front fender panel. The inner fender panel requires a rubber gasket which seals the fender area from moisture. It is very important that this gasket be checked and renewed if there is any question about its integrity. Most obvious is a gasket failure which leads to moisture invading the fender followed by rust. Less obvious is the need for this gasket to seal the joint where the inner fender panel, firewall and side rail intersect. The gasket must be cut long enough to cover a small traingular shaped opening at this intersection. The rubber gasket must fit tightly against the fender and at the bottom it must fit tightly against the outside rail cover. If not, moisture will find its way behind the firewall and then downward inside the rail. This seal failure is one important area to check on a regular basis to prevent having to do the kind rust repairs I faced.


Is this gasket related to the area I’m talking about or is it something else?




Paul Tomey
Tierra Verde,FL

1968 280SL Light Ivory (Enjoy)
2002 Porsche 996TT (Track)
2003 Van Dieman Formula Car (Race)
2006 Yukon Denali (Tow Cars and Haul Kids)

rwmastel

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Re: Box Section Rust
« Reply #1 on: August 03, 2007, 22:46:42 »
Paul,

Sorry to hear about your nasty discovery.  Are these missing places in the lip you feel up under from within the engine bay, or within the wheel well?  If you reach up over your front tire, you will find the horizontal box-section stiffner mentioned in your first quote.  You can see it with a flash light, helps to turn the wheel.

I would assume this rust is why the engine bay is painted black.  Someone tried to fix a rust problem then paint over it.  It's cheaper and/or easier to just use black then use a matching color, and people fixing rust can sometimes be the "do it cheap and easy" type.

I can't recommend an interim solution.

My recommendation for a long term solution is to frist make sure you know the extent of all the rust.  Have a body shop or restoration shop remove all that black paint to bare metal and dig deeper for rust.  A common serious place is the cross member in the firewall.  While you had your interior out, did you remove your rocker panels?

Finally, I believe that seal mentioned in your second quote is also in the wheel well.  I think it's located up where the firewall meets the fender, so it's not down by the floor board.  It could be covered in protective coating and hard to find.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420
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mdsalemi

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Re: Box Section Rust
« Reply #2 on: August 04, 2007, 07:32:03 »
Paul, Rodd et al.

Funny this should come up...

At Blacklick, Gernold took a good, critical look at my restored car.  Apparently he's had some issues with cars done after mine at the same place where some shortcuts were taken. (This was after the main guy had left and the place was in disarray)  Anyway, at various moments during the weekend he looked at peculiar places on my car, ignoring the very obvious places.

He noticed (I never did) that this area Paul refers to on my car is filled in completely.  There is no lip; run your fingers underneath this area and it is flush with that edge.  Both fenders had been replaced because of rust in this area and other areas on the fender.

I'm guessing that something like this had been done to prevent future rust by eliminating a collection point for water dirt salt etc.  190SL's rust here too.

If I can find a small mirror I'll put it underneath this area and you can get a better idea of what I'm talking about and I'll edit this post.

Michael Salemi
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Douglas

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Re: Box Section Rust
« Reply #3 on: August 04, 2007, 08:21:53 »
Paul,

Have you used a magnet on the body to look for rust? Generally, on a car with inner fender rust, it can be pretty pervasive.

Douglas Kim
New York
USA

ptomey

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Re: Box Section Rust
« Reply #4 on: August 04, 2007, 12:01:54 »
Thanks for the clarification Rodd. Now that I know where/what it is, this morning in the light of day I inspected both sides of the box section stiffener from inside the wheel wells. First, I can see why this is a weak point for rust, as the flat area on top of the box section would quite naturally collect road gunk and just sit there, possibly for years even if the car was washed regularly. Second, no surprise now, the gaps that I found from the engine compartment side go right through to the top of the box section stiffener. Also, the drivers side box has a few rust holes in the top of it. (I found the seal too, you’re corrected, it is unrelated to the area in question).

This morning I felt and poked (with an awl) and banged and scratched at every exposed part of the engine compartment and undercarriage, especially the cross member in the firewall and it’s all solid. I found an area rusted through in the drivers side headlight bucket and another area on the bottom of the cross member right behind the front bumper (see photo and feel free to tell me what that part is called).



When I had the carpet out and interior kick panels and quarter panels off to reupholster them, everything revealed was clean (original Silver Grey 180G). I always assumed that they painted the engine compartment and the underside of the hood black when they repainted the car Light Ivory. It would have been easier than correctly painting it body color and would cover up the silver in these areas.

Rodd, just out of curiosity, what made you ask if I’d removed the rocker panels during my interior work. I hadn’t thought to do it but, as it turns out I’m replacing the inner and outer chrome threshold rails and rubber and haven’t put them on yet so I’ll remove the rocker covers and the front wheel well inspection covers today and report back with more photos.

Michael, I could see where filling in the area inside of the wheel well would eliminate a collection point for dirt. Is that the part that you’re talking about or is it the lip that’s on the engine compartment side?

Douglas, most of what I’ve read points to this area as a weak point on our cars for rust, and I can see why. My interpretation of a “weak point” goes something like, “even a car that’s otherwise clean is susceptible to rust here.” You seem to be saying the opposite of that, “a car that has rust here probably has rust all over.” In any case I don’t plan to fiddle while Rome oxidizes. I’ll follow the trail where it takes me.

Quick fix is now off the table. I'm on the hunt. By the way it won't be a body shop or restoration specialist who removes that black paint down to the metal, it will be yours truly.




Paul Tomey
Tierra Verde,FL

1968 280SL Light Ivory (Enjoy)
2002 Porsche 996TT (Track)
2003 Van Dieman Formula Car (Race)
2006 Yukon Denali (Tow Cars and Haul Kids)
« Last Edit: August 04, 2007, 13:59:23 by ptomey »

66andBlue

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Re: Box Section Rust
« Reply #5 on: August 04, 2007, 15:22:08 »
quote:
Originally posted by ptomey

 ... so I’ll remove the rocker covers and the front wheel well inspection covers today and report back with more photos. ..


Paul,
be prepared that many of the tiny screws (Phillips #1 or even #0) will be rusted and difficult to get out.  Joe A. mentioned that he uses a "light duty" impact driver for such jobs such as this one:
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=93481
 Let us know how it went.

Alfred
1966 blue 230SL automatic
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rwmastel

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Re: Box Section Rust
« Reply #6 on: August 04, 2007, 16:40:41 »
quote:
Originally posted by ptomey

Rodd, just out of curiosity, what made you ask if I’d removed the rocker panels during my interior work.
Because I have heard that cars which look good often have rust here.

quote:
Originally posted by 66andBlue

Be prepared that many of the tiny screws (Phillips #1 or even #0) will be rusted and difficult to get out.
This is why I have not looked at mine yet.  I'm not ready for struggling with difficult screws because it makes a "simple" job into a longer one, more frustrating one.  Also, I don't know if I want to know what's under there!  Once I know, then I have to do something about it.  So for now, I don't know.

Rodd
Powell, Ohio, USA
1966 230SL, Euro, Auto, Leather, both  tops
1994 E420
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ptomey

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Re: Box Section Rust
« Reply #7 on: August 04, 2007, 16:58:41 »
The tiny ones (phillips #0's and #1's)came out easily. The one's on the bottom are stuck and want to strip. Looks like I'll be drilling them. The row along the top are rivited so I'll be drilling them anyway. I may not have pictures as soon as tonight but when I see what's under there, y'all will see it too.

Paul Tomey
Tierra Verde,FL

1968 280SL Light Ivory (Enjoy)
2002 Porsche 996TT (Track)
2003 Van Dieman Formula Car (Race)
2006 Yukon Denali (Tow Cars and Haul Kids)

Shvegel

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Re: Box Section Rust
« Reply #8 on: August 04, 2007, 21:01:04 »
It wouldn't make sense to pull the fenders(welded) just to replace the box section and I am sure it would be a nightmare to change without removing the fenders.

I would consider buying a new upper reinforcement and cutting the bottom off the 3 sided box. That would leave you with the outside and the top with the flange. You could clean it up as best as you could and glue the new section over the old with any number of body panel adhesives or you could use Urethane windshield adhesive which is pretty forgiving stuff. I glued a new floor in a rusty beater truck for a friend without any special preperation and it is still holding well after 7 years.

you could smooth over the seams(the urethane is like a caulk) and you would probably not be able to tell where the repair was.

If you try this DO NOT get the urethane on your hands etc you will not get it off. Wear rubber gloves!

ptomey

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Re: Box Section Rust
« Reply #9 on: August 04, 2007, 21:32:03 »
Since impatience is one of my virtues, the driver's side rocker cover is off and it looks just beautiful underneath! No rust, no corrosion, no filler just 1968 German steel hard as, well...steel. The rust you see in the picture is nothing, it will clean off with a scotchbrite pad.



I’ll check the other side this week but assuming it looks the same that leaves the other three areas that I know about so far.

Sidebar: I bought the car to restore it. It happens to run great and the exterior paint job looks okay at 50 mph so I’m going to drive it awhile, which is why I’m taking on the interior first. When it comes time to strip it though, I’m fully prepared to find rust and filler and deal with it correctly. I want to do as much of the work myself as I can including some body work and some welding… to a point -- no painting.

Since I know about the rusty box section stiffener, I’d love to hear from anyone who has ideas about how to fix it correctly. Also, same with the crossmember behind the front bumper (someone please tell me what that’s called).

Paul Tomey
Tierra Verde,FL

1968 280SL Light Ivory (Enjoy)
2002 Porsche 996TT (Track)
2003 Van Dieman Formula Car (Race)
2006 Yukon Denali (Tow Cars and Haul Kids)

Benz Dr.

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Re: Box Section Rust
« Reply #10 on: August 04, 2007, 23:27:55 »
This is a unit body car. Every single part adds strenght to the entire car. New parts need to be welded on. While pop rivets and glue may be OK for some things a main structural componet like a frame rail needs to be MIG welded on. This type of welding is stronger than the metal on the car and is certanly harder.
Patching this frame rail is almost impossible given the very difficult location. The only way to repair the innner renforcements is to remove the fenders which also involves the windshield. I'd wait to paint the engine bay and do the whole job all at the same time.
I've seen these rails completelt rusted away and yes, the rest of the car was very rustly as well. They become totaly unsafe to drive at this point. Nothing will save you in an accident - the car will fold up like a tin can.
 You sure you want pop rivets and glue between you and a tree, a rock or the other guy?

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Shvegel

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Re: Box Section Rust
« Reply #11 on: August 05, 2007, 01:10:38 »
Actually Dan alot of great advances in adhesives have been made in the last few years. When I was teaching Mechanics for BMW a couple of years ago they Introduced the E60 5 series Which featured an Aluminum front structure GLUED to a Steel passenger cage and rear section. I believe they went back to an all steel structure a couple of years later because body shops were unwilling to invest in the equipment needed to properly repair the aluminum front structure.

This stuff isn't Elmers Glue and it certainly would be stronger than a rusty rail. As for windshield urethane it is the primary reason that Windshields and rear glass are now a structural element of the car. In fact if you replace a windshield and allow the urethane to cure on uneven ground it can actually cause the car to acquire a permanent twist.


I am with you on Pop-Rivits It's a very rare day when I pull that tool out of the box.

Shvegel

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Re: Box Section Rust
« Reply #12 on: August 05, 2007, 01:40:10 »
Ptomey,
It also sounds as if your car has a similar pattern of rust to mine.

The front crossmember comes in 2 pieces from Mercedes and is a fairly straightforward operation to weld a new one in. It is a little difficult to slip out from under the lower part of the nose assembly but it can be done. It might be a good first welding project with a little help from someone who knows the way.

If your car does follow my pattern I would remove the inner fender splash shields(which would be a good time to change the rubber seals) and check the area on the front of the rocker panel closely.

For what it is worth I have used the small Lincoln MIG welders alot and they will take a ton of abuse and keep on doing their job. I once welded 1/4" steel plate nonstop for 12 hours without a lick of trouble on a model SP 125. I would buy the best 120 volt unit you choose to afford.

You seem to be approaching this as a project. If you find rust in the rocker assemblies you might want to consider finding a cleaner car to start with. I am 1 year into restoring a once butchered rusty car(replacing front box sections, inner aprons, rocker assemblies, rear quarter panels rear pane, trunk floor and inner wheel houses) with no end in sight and by the time the body work is done it will cost me well over 15k.

ptomey

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Re: Box Section Rust
« Reply #13 on: August 05, 2007, 09:00:25 »
Shvegel,

Thanks for your response. I'll check under the splash gaurds and renew the seals while I'm at it.

So the replacement box rail has a flange on the top like it does on the bottom...I understand your method of replacing it. Have you done this? If so I'd like to pund you with a few more specific questions but for the meanwhile, how would one address the metal which is missing from the top of the inner wheelhousing under the lip of the fender? The part that mates up to the flange on the box stiffener?

BTW, I have had a Clarke 120V MIG welder and done some minor projects, shop stuff, trailer repairs and none structural stuff on my race car (brackets, etc.).

Paul Tomey
Tierra Verde,FL

1968 280SL Light Ivory (Enjoy)
2002 Porsche 996TT (Track)
2003 Van Dieman Formula Car (Race)
2006 Yukon Denali (Tow Cars and Haul Kids)
« Last Edit: August 05, 2007, 09:03:46 by ptomey »

Shvegel

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Re: Box Section Rust
« Reply #14 on: August 05, 2007, 09:05:14 »
Could be worse...



Download Attachment: 777.jpg
14.9 KB

Download Attachment: 778.jpg
18.48 KB

If you ever get discouraged this helps.

http://www.classicsl.com/newpage110.htm

ptomey

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Re: Box Section Rust
« Reply #15 on: August 05, 2007, 14:28:13 »
Of course things could be worse! I found 3 areas of rust on a car that I plan to restore! Dan's got me folding up like tin can after getting hit with a grocery cart in the parking lot of Publix!

Seriously, how do you get those splash guards off? I see the bolts but are they on there with some sort of adhesive too? Who's done this recently?

Also, as far as I can tell, removing the splash gaurds (inspection covers?) is not going to reveal anything more about the rockers because they're up too high. In any case, I'll let you know what's behind them (Except you Dan  ;) ).

Paul Tomey
Tierra Verde,FL

1968 280SL Light Ivory (Enjoy)
2002 Porsche 996TT (Track)
2003 Van Dieman Formula Car (Race)
2006 Yukon Denali (Tow Cars and Haul Kids)

George Davis

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Re: Box Section Rust
« Reply #16 on: August 05, 2007, 16:00:17 »
Paul,

I had some repairs done on my car and one involved the box section stiffener inside the front wheel wells.  Because of the shape of the stiffener and limited access under the fender, I think it's not possible to weld the upper flange with a MIG welder.  The stiffener and flanges form a "top hat" shape.  The guys who did my repairs cut the stiffener lengthwise down the middle of the "top of the top hat", and then welded the upper section on the inside of the upper section, basically where the brim joins the side of the top hat.  They then welded the lower section in and welded the upper and lower sections together along the cut.  Much easier than removing the fenders.

In the situation discussed here, it may make sense to remove the old stiffeners, do the patching from inside the fenders, then install new stiffeners.

Good luck with it!

George Davis
'69 280 SL Euro manual

Benz Dr.

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Re: Box Section Rust
« Reply #17 on: August 05, 2007, 16:39:30 »
Well, you're right about modern epoxys used on many cars today. They simply glue the door skin on and it's pretty strong or they wouldn't be able to pass new car regs. As for frame rails, I prefer them to be MIG welded on. The factory used spot welds which are also very strong but they were using clean steel. I've used my spot welder a bit but found it just wouldn't work unless everything was clean and set up perfectly.

There was a time when everyone used  brazing rod to hang body pannels. This works but not all that great. I've seen a lot of older restorations with brazed in frame rails - not good. I only use that stuff to fill in small holes in water pipes or other minor repairs. I'm also just as likely to use JB weld if I want a cold weld repair. I agree though, modern expoys are fantasic.

Dan Caron's
 SL Barn
benzbarn@ebtech.net
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1966 230SL 5 speed, LSD, header pipes, 300SE distributor, ported, polished and balanced, AKA  ''The Red Rocket ''
Dan Caron's SL Barn

1970  3.5 Coupe
1961  190SL
1985   300CD  Turbo Coupe
1981  300SD
2013  GMC  Sierra
1965  230SL
1967 250SL
1970 280SL
1988 560SEC

ptomey

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Re: Box Section Rust
« Reply #18 on: August 06, 2007, 19:20:08 »
George,

Thanks for the reply. Yes, this is the second time I've heard of that exact method for replacing those babies. Definitely beyond my welding abilities.


Paul Tomey
Tierra Verde,FL

1968 280SL Light Ivory (Enjoy)
2002 Porsche 996TT (Track)
2003 Van Dieman Formula Car (Race)
2006 Yukon Denali (Tow Cars and Haul Kids)