On my list, but after all my kids finish college (one is in med school). Then a CNC machine, etc, until my wife screams. You are right about buying on craigslist. With a quality product you can usually sell it for close to what you paid after using it a few years, kind of like a cheap rental. I have bought many things that way, and all the sellers seemed to be people like me, not the stolen stuff one worries about.

I am going to state my position more directly.

I think this was a safety issue important enough that you should have rented a proper welder.... or paid someone who could do it properly ....

It is like the member who drove their car home without a fan belt.... to save an $80 tow bill. He risked burning up his engine to save a relatively small amount of money. A suspension fix that is not absolutely right on the money risks much more than a tow fee.

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/diesel-discussion/10414-help-i-need-check-stretch.html

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Usually a matter of judgement on deciding on what can be repaired properly and what cannot. For example I believe for quite some time welding repairs are a no no on many newer cars. Changes the temper of the high stress steel in the welding areas. They have sacrificed metal gauge for thinner but stronger varieties of steel.. Fatigue repairs in one area may indicate the onset of more in similar areas later. One reason I do not like cars with really excessive amounts of milage. Fatige failure incidence may increases with it. .

Fortunately when rust is getting to the point of being seriously structural. The general overall condition makes repairs really questionable. Nothing much really solid left to reach. Doing it right becomes a major enterprise. I have tackled a few really difficult very time consuming issues before. I would not do it again today. Just too much work.

I for example really dislike the set up under the front end of 126s. When heavy rust is present. Losing steering is worse than brakes as you are at the complete luck of the draw usually if it occurs. All those old 114 and 115s steering box mounts should be periodically checked. Up here in the rustbelt I have had to repair a few of them we owned.

Barry,
You have brought up important issues which deserve to be in this thread.
The characteristics which are incorporated into the steels chosen for important parts in a car are compromised by welding.... even if strength is still sufficient .. corrosion resistance is almost always gone.... I argued this when suggesting that overlapping and plug welding and rivets ( not the pop type ) be used when installing complete new floor pans instead of welding the entire circumference. You do not want a floor pan holding your car seat to rust enough to drop you on the ground at speed....

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

Excellent points. The K-frame in my 65 Dart looks like 1/8"th steel, compared w/ maybe 1/16" in my W123, and the lower control arm attaches into a thick tube in the K-frame, plus you can unbolt the K-frame (4 bolts) for an easy swap. Still, there is a lot of margin in both. I have seen photos of cars with the bottom totally rusted, yet the cars somehow stay together and can even drive. The thin galvanized steel they starting using in the 1980's seem to last fine in the west. I have no rust in my 300D's. The photos I see of cars in Canada and Northern Europe are shocking to CA & AZ owners. I wouldn't worry about your seat falling thru a rusted floor pan, since there is plenty of frame below to prevent that (transmission cross-member, ...), plus such failure is usually gradual. Metal fatigue is the ultimate threat in all vehicles. Many fret over that in large airplanes, for good reason. Many actual fatigue failures and structural failure is of much greater concern there.

Someone might research what has happened when a K-frame, control arm support, ball joint, or steering linkage has broken in any car. My guess is that usually the car was somewhat steerable. If the engine touches the pavement, that provides braking, and sparks are safer w/ diesel fuel. If you jammed on the brakes and locked up all 4 tires, the car should just skid to a stop, in a fairly straight line (I watched a fool do that in an interstate lane next to me when a front tire blew at 65 mph). Passenger cars are fairly immune to roll-over, unless you slide down a steep embankment. Can't say the same for SUV's and pickups.

I think one of our members actually had the seat start to fall through.. He was from Houston...
I was under the impression our cars were mostly unibody... thus no real frame as in the old days...
the rusting is gradual.... but the actual failure can be very sudden... as when going over a rough railroad crossing... and the worst part is that you are not expecting it...

__________________
1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/diesel-discussion/156207-photo-step-step-post-showing-w123-evaporator-removal-1983-240d-1982-300td.html?highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html

I got bored at lunch, so decided to take up my request to find what has happened when a lower control arm failed. Stories about cars in the links below. I skipped the common off-road failures in SUV's and trucks.

Broken Lower Control Arm - Appearance - Red Pepper Racing
Lower Control Arm Fails-BOOM-Rust. Need tips on repair. - MBWorld.org Forums
Broken lower control arm on my M3
1996 E300D front control arm collapse | Mercedes-Benz Club of America
Ever had a lower control arm break? - Chevelle Tech

In my "get 'er home" trip, I was only worried about keeping the LCA "pivot cup" in position, since if it moved outward again the right front wheel would toe-out. The chain (2500 lb break strength) pretty-well assured it could not rotate outward. The cup was still solidly attached to the K-frame (other than for tilting). The LCA in our 300D's appears to be solid forged steel, not the wimpy welded sheet-metal one sees in many cars.

For some cars, it seems that LCA breakage while driving is not uncommon (many "mine broke too" comments). Sounds like mostly metal fatigue, since often happened on fairly smooth pavement. In all cases, the suspension and front tire simply dragged on the ground until the car stopped. They didn't drift into another lane or roll over. Many scarier things one could worry about while driving. Perhaps a little gunk or rubber hose bit plugs the spool valve in your power steering gear, making it decide to steer hard left. Could you over-power it? Always belt up.