I am trying to keep my rad from falling out! The lower cross member (rad support) has almost completely rusted out at the outer edges.I just picked up a new one from the MB dealer (CAN $63)and looking at it and the car it would appear that it's welded at the outer edges.There is also a bracket in the middle that seems to be welded to the crossmember and it goes up behind a trim panel that hides the upper part of the crossmember. Is that trim panel welded on as well?How involved is this job?My neighbour has a welder (stick & mig)and I realize the rad has to come out but I will only have the weekend to complete the repair. Anyone else done this repair? Please advise

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

Kyle:

I've never really looked that close at the lower radiator support on a W123! It will be spot welded onto the rest of the body at the flanges (about 10mm wide) on each edge where it attaches to something, about 25mm apart. Trim, unless steel, will the screwed or clipped, not welded.

If it is really rusted you can split the old on off the good metal with a chisel, then drill holes in either the old or new part where the welds were, then weld the holes. If you can reach the all the flanges, you can also grind the old one off rather than split it off by grinding through the spotwelds.

The other alternative is to drill out the spot welds -- this both frees the old part and sets you up to weld the new one in place. Some parts are also seam welded, but this is rare.

Wire feed welder set for sheetmetal is best -- stick will probably just blow holes in the metal unless the amperage can be set low enough. Use 0.023" wire or very thin rod.

You can also cut part of it off if you need to, then butt weld the old and new parts together. This is more difficult, you may want to practice on scrap first.

Do disconnect the battery and alternator while welding -- you can reverse-load the battery and fry the diodes in the alternaltor!

Figure a couple minutes for each spotweld to drill or weld, and plan on plenty of extra time for discovering that things aren't going quite to plan.

I would recommend finding some spare sheetmetal the same thickness as the parts -- you may need to fabricate some extra bits with a set of shears and a ball-peen hammer.

Good luck!

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

I appreciate the advice though I think I'll leave the welding to my neighbor ! After I read your reply I looked at it again and I think it's put together just like you describe. There's just so much metal missing it was hard to tell. I'll post a follow-up when I get around to fixing it in a week or two.This is a great forum

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

I can identify with that! I learned a whole lot about fabricating sheetmetal from my brother whilst fixing his 75 300D -- he's pretty good (learned from the old guy down the road 20 years or more ago, including lead filling!). We make a trunk pan, rear floor pans, and a fender tip for it, and it looks pretty good. The pans are obviously hand fabricated, but the fender tip will probably pass for factory when we are done.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

welding thin sheet metal can be done with a stick welder after about thirty years welding experence.that is an exaggeration but not by all that much.psfred is right it is quiet easy to destroy your alternators diodes welding on an auto with an electric welder especialy when welding that close to it, you can take the battery cables off the battery the connecting wires off the alternator or best take the alternator out of the car when welding electric welding can also be death to a computerized car,I often braze or gas weld for this very reason.
William Rogers.....

I finally got around to doing it last weekend,after pulling the rad to do the vaccum pump I could see that my rad support wasn't.The fix was straightforward with the two 'console supports'that are spot welded to the frame and the rad support is spot welded to them.With all the factory parts(rad support,left and right supports,$100Cdn) we removed one support at a time by drilling the spot welds almost out and then pursuading the bracket off with an air chisel.Once the supports were in we tacked the rad support in and test fit the rad and oil cooler(there's a lot of adjustment side to side),got it perfect the first time and everything went back in like it should .This weekend,now that the paint has cured,I'm going to seam seal the area and undercoat it so it lasts a long time.It's nice to close the hood and not wonder if the rad just dropped down

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

Kyle:

contrats! glad to hear it worked out fine.

One nice thing about MB -- they tend to build major components out of smaller ones. A bit fiddlesome sometimes, but it allows repairs without extensive fitting. My brother just fixed a fender on his 75 300 -- drilled out the spotwelds and removed the headlight bucket, pounded out the dent (originally completely filled with Bondo!) and spotted it back in in an evening.

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!

Thanks Peter,it was a job I don't think I would have contemplated doing before,but I figured even if I got in over my head someone(like you )would be able to give some more direction.I now feel confident to start on the rocker panels,I have some delamination of the undercoating around the jacking holes.BTW what is the primer that MB uses?That stuff was like brand new and very tough under the spot welds.Even the new parts were coated in it,at first I thought it was just a shipping primer but when I tried to strip it to weld to I found it was really on there.Now someones going to tell me that it's weld-through primer

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Democracy dies in darkness, you have to kick at the darkness till it bleeds daylight

Kyle:

I don't know what it is, but it is great stuff. Same as Volvo, I think (white on the volvo) and simply never goes bad. All the rust I've seen so far on MBs is from badly sealed seams or water standing in the interior, almost never see rust from the outside, at least on the newer models.

I don't know if you can weld through it or not -- you can always grind some off if you need to. See if you can get some from MB for re-painting, too -- probably expensive, but far better than autoparts store stuff.

Get some seam sealant, too -- the stuff MB uses to fill body gaps. Wonderful stuff, stays flexible like their undersealant but thicker.

If you are replacing lower fenders, get the tool to make an offset to set the new panel in -- we butt welded the homemade panels here, and it is a pain. Much easier to make the offset and drill/plug weld the new panel in place -- less heat and less distortion. Fill the inner side with MB sealant and lead fill the outer if you can -- if not, Bondo will do, but lead is better.

Have fun!

Peter

__________________
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!