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  #1  
Old 01-14-2004, 07:36 PM
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How to fix a broken control arm pivot?

Yesterday I discovered that my '73 280 (W114) had broken its driver side lower A-arm pivot off the cross member. You can see in the attached picture that the rear part of the pivot is completly broken off and the front part is about to go.
Has anyone gone through this fix before? Can I weld the pivot back onto the cross member? Or do I need to replace the whole cross piece? It looks like I'd have to pull the engine to replace the cross member. I don't want to do that!
Is this a common failure?

MOOSE
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  #2  
Old 01-14-2004, 07:38 PM
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I don't know what happened to the picture. I'll try again.

MOOSE
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How to fix a broken control arm pivot?-broken-benz-1-resized.jpg  
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  #3  
Old 01-14-2004, 08:14 PM
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I haven't seen or heard of this problem before. You might be able to weld the original contol-arm mount back together. You may need to fabricate and add reinforcements to the repair. It all depends on how good a welder/fabricator you are and if you believe you can make a reliable repair with the crossmember (also kown as a 'subframe') installed in the car. If you have any doubts, you would be better off replacing it. Wether you decide to repair or replace the subframe, it's possible to fabricate an engine support bar and chains to straddle the inner wheel housings or front fenders (fenders heavily padded with thick telephone books of course) and remove the subframe while the engine remains in the car. If you wind up removing the subframe, that would be a good time to replace any bad mounts. Good Luck.

Happy Motoring, Mark
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Last edited by Mark DiSilvestro; 01-14-2004 at 08:26 PM.
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  #4  
Old 01-14-2004, 08:59 PM
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If this ever happens at all, it's usually on account of rust - say on early Ponton models or even the 116 that also suffered rust.

I hate to say this, but you should probably be thinkin about getting another 114....... or takin the car to combination welder/mechanic who knows how to remove and reinstall the A-frame and make the weld stick like glue - all for whatever reasonable price you are willing to pay.
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  #5  
Old 01-14-2004, 09:08 PM
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Another pic. From the rear looking forward.
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  #6  
Old 01-14-2004, 10:11 PM
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In 1976, I had a similar problem, the failure of the threaded subframe steering box mounts on my '61 Ponton 180b. My factory Ponton shop manual stated that if there was any doubt as to being able to reliably repair the subfame, it should be replaced.
Yours looks like a fatigue failure, not rust.
The crossmember/subframe is detachable, not part of the unibody so, worst case scenario, you'll have to replace it with a good used or new one.

Happy Motoring, Mark
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Last edited by Mark DiSilvestro; 01-14-2004 at 10:19 PM.
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  #7  
Old 01-15-2004, 12:59 AM
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Location

Where are you located....I have a 115 that can be had very reasonable.....
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  #8  
Old 01-15-2004, 12:13 PM
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You also need to replace all the control arm bushings -- the one in the pic is missing most of the rubber, and probably the fracture was a result of the bolt and sleeve banging around inside the hole.

Peter
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  #9  
Old 01-15-2004, 01:39 PM
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I feel for you. This is the same way I learned to weld. My son got his 65 Mustang and after taking it apart I discovered that I had to weld about 12 sections of the car. This looks to me like it can be repaired. I would consider completely removing the mount from the subframe ( if this car is a subframe moount setup other wise your forced to repair the mount ) so you can check the interior of the subframe. It may need some rust treatment. And then reattach the mount by welding it back on.

Another option is to of course find another subframe mount and just swap it out.

Try to find a good restoration shop in your area and they will be set up for repairing the subframe. Or I recommend Lincoln electric, Hobart or a Miller welder. I have the LE weld pack 100 with gas conversion. If your going to do your own welding go with a good name brand welder not a knock off. It will last forever and you'll be happy with it. Don't over buy a welder. I was going to buy a LE unit that was 2 steps up. when I called LE to ask some questions the salesman talked me down to the bottom unit. I have been able to weld anything I have and some freinds stuff on his Mustang and Corvette without any problems.

Dave
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  #10  
Old 01-15-2004, 05:31 PM
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Peter,
That makes sense. No wonder the subframe broke. I'll get some bushings on order from Claridges.

Dave,
I'm going to rent a wire feed unit from Home Depot. They have 'em for 30 bux a day. Probably have to buy a spool of wire too. I'll spend half a day practicing on scrap, then go for it.
Thanks for the encourgement.

MOOSE
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  #11  
Old 01-15-2004, 07:18 PM
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Or replacing the entire subframe might be path of least resistance instead of making welds that might not hold.... Hell, at good junkyard you could probably walk away with fresh A-frames too.... and they will cut the replacement subframe out in matter of maybe 30 minutes otherwise itsa bolt on part when you go to install it.

Long time ago, i was dealing with broken rear subframe on 114.... the huge wishbone looking thing that holds rear suspension to the unibody. Believe it or not - it was notso difficult to replace. Toughest part was dealing with coil spring compressor.
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  #12  
Old 01-16-2004, 03:26 AM
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I hope you're not driving the car. While you're working on the subframe, check for oil leaks as well.
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Old 01-16-2004, 03:26 AM
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