W123 Structural Repair - Front Jack Point - need some help
 

I have a thread going in the Bodywork forum, but it isnt too well traveled over there. I have gotten some great advice so far, but I wanted to get some more opinions before I 'operate'.

This is the 85 300D. I went in to clean up some rust that turned out to be big. See the first two pics. A forum member cut out a big rust free chunk of the front jack point for me to weld in.

Question is: How much should I cut to stitch in the new piece? What would you do? Im trying to do this 'right'. The rest of this car is great and it will last a long time.

That jack point itself is not rusted, but the metal all around it is, as you can see in the pics.

First a couple shots of the cleaned up rust:

http://i414.photobucket.com/albums/p...8/IMG_0491.jpg

http://i414.photobucket.com/albums/p...8/IMG_0492.jpg

Now some side by sides of the piece against the infected area:

http://i414.photobucket.com/albums/p...8/IMG_0493.jpg

http://i414.photobucket.com/albums/p...8/IMG_0494.jpg

Rear View
http://i414.photobucket.com/albums/p...8/IMG_0495.jpg

Top View
http://i414.photobucket.com/albums/p...8/IMG_0490.jpg

Thank you for the advice.

Original thread:W123 - Advice needed on jack point rust - PeachParts Mercedes ShopForum

dd

I'd say cut out as much of the orginal metal as you need to fully fit the new piece in.

Usually, i'd say keep the original metal, as most 'patches' are stamped using thinner metal, but this is from another donor car, so that point is moot--as they are the same quality/thickness of metal.

looks like a big job, personnally I wouldnt go near the door pillar and hinge point if you can avoid it. also replacing the whole piece would leave the area weak and easy to twist or get out of line unless you happen to have a frame rack in your garage. start cutting out rust until you hit good metal leaving as much of your car as you can within the size of the donor part then fit in the patch pieces from the donor piece. if two rust areas end up getting close to each other and leaving a thin rib then start looking at bigger patch pieces

ah , yeah i didnt look closely enough. In that case, id make the patch smaller and leave your car the same, as this is an important structural part...

What you have left looks pretty sound to me and I don't think you have lost much, if any structural integrity. I would just fix it cosmetically with the new metal you have. I would not cut anything back any further (do not mess with the A-pillar), just get to clean metal. I know you just bought a MIG welder, so you will want to use that, but if it were me I would use this stuff:

http://www.lord.com/Home/ProductsServices/Adhesives/FusorAutomotiveAftermarketProducts/Products/MetalAdhesives/tabid/3400/Default.aspx

I have used quite a bit of this over the last 5 years and it holds up well. The nice thing about it is that it does not promote additional rusting at the weld that you might have with a MIG weld.

Rick

I would not want to touch that A pillar either.

Be sure to clean out all that waxoyl with mineral spirits before you try to weld!

Ditto on everyone who said don't touch the pillar. Cut around the bottom of it.

Good pictures by the way.

dd,

ill respond in your otehr thread tonite

Thank you for the replies guys.

Im glad to hear that the consensus is not to cut the A pillar. That really made me nervous. If it was executed *perfectly* and TIG welded I bet it would be best - but this is the first time I have welded so I dont want to get in any more over my head.

"Be sure to clean out all that waxoyl with mineral spirits before you try to weld!"

bgkast, good idea. I guess it would seem obvious, but I am going to need to get all of that stuff out, right? It will ignite easily? Is there any good way to replace it after the fact?

thanks again guys. i would have never dreamed of attempting something like this without knowing i have the forum to ask about it...


dd

Structural Repair
 

Hello there, I'm from Rhode Island , and I have worked on several of these cars over the years and I have a w116 in my shop now doing a total restore, from my own experience I have almost always found rust to be attacking behind the rockers , behind the brake booster, and behind fuse box and what you will have to do is measure what you have to work with and only cut the rust porsions out, then take the peace you have for repair and do and exact mesurement .. Cut to fit, you might have to cut some small metal patches and weld them so everything lines up. take you time and study what you need to do.I personaly would pull the rubber plugs out from under the door threshold plate and spray a sealer inside with a long wand to stop all internal rusting, also you should be able to see how much rust is in the rockers after you cut bad out..lay it up the and mark it and then measure and cut to fit. take 16 guage metal and form it around that courner lap it around put some tempory rivets to hold everything in place, once you have everything lined up and you know it is right and ready then weld it.it doesn't have to be welded all the way it only supports bottom door hinge, but weld most of it, then you can take some epoxy and mix it up to seal it, remember to much will more then likely have to be sanded down so the door will fit propely. you can grind the epoxy down just like bondo or any other body feeler, But epoxy is very strong and the way to go, nothing is exact here except for the lower door hinge, everything else will be hinden behind fender,use a good sealer when finished only after the door is restalled for fit... good luck and let us know , how it works, its a whole day job and tedius work.good luck, Jerry

structural repair
 

PS the Jack holes are not open to the inside, in other words they do not go all the way inside the rockers, closed on the ends, so all rust starts from the inside out water gets in and doesn't drain properly, it should stay dry on the inside so water was getting in behind from somewhere, more then likely brake booster and then travels down, thats my take of this, pull you booster and tell me what you find? Jerry

don't cut the hinge pillar
 

just cut the rust out , leave the hinge alone., I would not even use, that donor peice , just cut the rust out and weld you a 16 guage patch and seal with epoxy. then seal inside rockers with a good sealer spray it in witha wand .Sorry I looked at it closer.Jerry

I disagree with sealer in the rockers. Rockers are tricky when you can get to little spots of surface rust. Sealer won't seal rust in my book, all it does is hide it temporary and speed up the rusting process by lifting and holding moisture in. Spray bar an chain oil in the rockers, this will stop the rust!

For rust holes I find its pretty easy to use manilla paper like from a folder to make templetes, you can use cardboard also its just thicker to work with. Freehand it in the hole with a marker, cut the templete, then use the marker to trace the templete onto sheet metal. You woul be amazed at what you can build if you take the time.

On my 300TD winter bomb that I'll be starting on soon in my garage, I think I may just close off the jack points.

Wow what a fantastic set of pictures!

@dieseldan what happened? Have you get anymore pictures?

Take only what you need from the donor patch. My car needs the same repair. I went to a junkyard recently and started cutting out that section from a rust free car. The car started collapsing as I was cutting out a large section! Be careful!