85 300D rear wheel well rust repair - Page 2 - PeachParts Mercedes-Benz Forum

Stretch · #16 08-31-2012, 10:32 AM

Quote:

Originally Posted by Graham

I haven't checked with local dealer, but US based on-line dealer wants about $40 per bracket.

I have a shop that will do the welding for $50/hr, so it may be worthwhile buying the brackets if he decides they need replacement rather than repair. I am sure it will take more than an hour to make a bracket!

Anyone hazard a guess as to how many hours for weld repair job assuming same work on both rear wheel wells?

Well that's not a bad price. Well it isn't as bad as I thought it would be. MB dealer prices are funny - some times they seem to be totally out of whack but I doubt if you could pay someone to make one cheaper in this case.

As for the time taken to fix it to the car I would hope that they would manage to do that within a couple of hours!

JamesDean · #17 08-31-2012, 01:13 PM

Graham,

Check out my links here, you might find something useful in there:

http://www.peachparts.com/shopforum/body-repair-restoration/288453-300sd-rust-restoration-project.html

http://www.peachparts.com/shopforum/body-repair-restoration/304380-300sd-rust-restoration-project-2-a.html

Graham · #18 08-31-2012, 03:23 PM

Quote:

Originally Posted by JamesDean

Graham,

Check out my links here, you might find something useful in there:

http://www.peachparts.com/shopforum/body-repair-restoration/288453-300sd-rust-restoration-project.html

http://www.peachparts.com/shopforum/body-repair-restoration/304380-300sd-rust-restoration-project-2-a.html

I have read your links in past. But I hate seeing all that rust

My 300D is not as bad despite having lived and been driven in a salty environment for most of it's life. The rust treatment most of us have done annually up here must be helping

zu! · #19 08-31-2012, 08:09 PM

Quote:

Originally Posted by Army

Never ever ever use a pressure washer on the underside of a car if you are in a damp / wet climate. You will manage to push water into more places where it shouldn't be.

I don't have a quick solution for cleaning the crud off of the underside - I use engine de-greaser and careful scrubbing with a brush. The best way of removing the stupid rubber Mercedes factory fitted undercoating is to use a powerfull hot air gun / blow torch with a rigid paint scraper (the type you'd normally use on window frames).

If the metal is rusted underneath you can easily remove the undercoating with your fingers - if you were to use a pressure washer you'd blast straight through it; possibly past the rust or through it pushing water into places where you can't dry it out. If water gets between the spot welded joints on these monocoque constructions you may as well kiss your car good bye.

I never thought of it that way! Interesting observation though. I had a rust hole appear seemingly out of nowhere on my left rear dogleg. It just looked like a bubble the size of a 25 cent coin. I poked it with a screwdriver and it ended up with this huge hole almost the width of the dogleg! Further poking revealed a another hold on the inner side of the fender. How water got in there is beyond me....but it could've been because of years of pressure washer usage on the underbody.

I would like to tear off that underbody rubbery thing as it as started cracking here and there. Not sure if its advisable though.

Graham · #20 08-31-2012, 08:20 PM

Quote:

Originally Posted by zu!

1984 300D
586,000 KM and going strong
BC Canada

It could be that your car (and mine at 430k km) are past their "best before" dates?

I am going to see if I can clean off the rest of the car before I take it to shop for welding. Just in case there are any other bad spots. I don't mind the ones in non structural flat areas. I have used POR15 and glass to make repairs that seem to last indefinitely. Or at least for 22years and still good!

Stretch · #21 09-01-2012, 06:20 AM

Quote:

Originally Posted by zu!

...
I would like to tear off that underbody rubbery thing as it as started cracking here and there. Not sure if its advisable though.

I consider it to be a race against time - if you've noticed that crackle effect I think you are better off investigating rather than not. At least when it gets to the crackling stage it is easier to remove - otherwise you're using hot air guns or blow torches to get the rubber stuff off. Then you have problems of things getting damaged on the other side of the underside...

...there's no quick and easy fix that I know of...

Graham · #22 09-01-2012, 09:39 AM

Has anyone replaced part 74 in the picture below? It is the backing plate for the torsion bar bushing clamp.

They sell it as a spare part, but what is not clear, is if it ends up being welded in place or sits loose inside the frame. There is a slot with rubber plug adjacent that looks like it could be used to slide the plate in.

In my case, after a bit of cleanup, the plates appear in good condition and I can remove the bolts. But if we weld repair the sheet metal that encloses those plates, then they will likely be in there for good! Which might be OK if they last another 27 years

. But maybe they are already welded in?

Graham · #23 09-04-2012, 08:35 PM

In attempting to unbolt the rubber buffer in the pic below, the whole bracket came away

There is still good metal about 6" back, but it's going to be tough to do a weld repair with the spring so close behind. ou can see a piece of the bracket's tab at the bottom right of the pic. It was not connected!

Stretch · #24 09-05-2012, 05:12 AM

Oh no!

I think it might be an idea to remove a lot more of the undercoating to see if there's any more rust hinding under it.

I expect that people who live in dry climates will be thinking scrap it...

...whereas those of us in the wet will be thinking...

...Oh no!

JamesDean · #25 09-05-2012, 09:07 AM

Quote:

Originally Posted by Army

Oh no!

I think it might be an idea to remove a lot more of the undercoating to see if there's any more rust hinding under it.

I expect that people who live in dry climates will be thinking scrap it...

...whereas those of us in the wet will be thinking...

...Oh no!

+1 Remove a lot more undercoating see how far down the rabbit hole it goes.

barry123400 · #26 09-05-2012, 11:00 AM

Quote:

Originally Posted by Graham

Have the rubber cut away on other side, but haven't tried heat yet. Have a feeling the rust will mean that in the end I will have to drill

In rust prone areas of north america heat is almost indespensible to deal with fastenings. I would never work on certain areas of cars in my location without a torch set being present or available. Some simple tools like nut splitters are very useful as well periodically.

Somewhat less so in Ontario but only in degree. Now if you want a really agressive penatrating oil a 50-50 mix of acetone and transmission oil will help but you have to be patient enough to let it work. Applies to all decent penatrating oils really.

This is okay unless you are in somewhat of a hurrry. The home mix is far more effective than commercial penatrating oils. Personally I still find serious heat my best option usually.

Graham · #27 09-05-2012, 03:45 PM

Quote:

Originally Posted by Army

Oh no!

I think it might be an idea to remove a lot more of the undercoating to see if there's any more rust hinding under it.

I expect that people who live in dry climates will be thinking scrap it...

...whereas those of us in the wet will be thinking...

...Oh no!

I have gone over the complete wheel well areas and the metal is solid with no undercoating delamination.

But bad spot is on back side of the section where the rubber buffer support attaches. In order to repair the back area near the spring, I think the front side will have to be cut away to provide access - maybe about 1sq.ft. Then new steel will have to be welded on inside and then on the front. Finally, a new bracket will have to be made and welded in place. Will have to see what the shop says.

One other option would be to buy a complete new section from MB and just use the part that is needed. Still hard to weld the back section though

Graham · #28 09-05-2012, 03:47 PM

Quote:

Originally Posted by JamesDean

+1 Remove a lot more undercoating see how far down the rabbit hole it goes.

About 4-6" down the "rabbit hole" the original factory Waxoyl is still there. If the spring was removed, it could easily be repaired, but that would be a bigger job!

Stretch · #29 09-05-2012, 03:59 PM

I think you are far enough into this project to consider sub frame removal. It isn't as bad as you might think. Have a look at this thread

http://www.peachparts.com/shopforum/diesel-discussion/276507-rear-subframe-removal-bushing-replacement.html

and tell me what you think.

As for your repair plan of attacking the inner wheel arch in order to make a strong repair - I think that that is a really good way to go. It is really difficult to replace those inner wheel arches as whole panels (which is arguably the best job possible => replace like you are at the MB factory!) but to get to them you need to remove the outer wing / fender...

http://www.peachparts.com/shopforum/body-repair-restoration/303669-my-w123-saloon-sedan-old-accident-repair-bit-rust-repair-thread-3.html

Repair panels are available to help you with the inner wing. They are made by Klokkerholm. They're not the best looking panels in the world - but they are better than nothing. The last time I looked the original MB panels are also available although not the long chassis rail-like things you put in your last picture.

Alastair · #30 09-05-2012, 05:08 PM

You could do it the way I did a similar piece on mine (It was an area approx 6" forward of yours, extending to 18" of the sill area around the subframe)

Cut the outer sheet-metal away first, giving yourself lots of room--be generous with the amount removed, trim the inner back to good metal, then welding in new steel shaped to an 'L',--with the lip facing out, then replace the outer in the same way, with the lip facing inwards welding the inner to the outer to form the 'box'....

Make sure the welds are continuous, or at the very least, every 1/16 inch....

Coat after cleaning with Etch-Primer, Top-Coat and Shutz.

Job done, without having to remove the Subframe...

Finally, look up inside rear of subframe along the rails find the plastic plugs, and shove loads of Waxoyl in there....

Also, remove the rear outer seat-belt bolt at the floor and shove around a litre or so of Waxoyl in there too--This is directly into the sill area and will spread the length of the car....

Job's a good-un as they say....