Attention all W126 owners....beware of rust at the sway bar frame mounts. My 1991 300SE was believed to have only rust spot on the front fender and clean underneath. While replacing the smog pump I found some suspicious puckering on the undercoating. After some digging here is the sad reality. Now I am looking for someone to trim away a little more and weld up these areas. Note that both of these spots have drain hoses right next to them. I suspect that the undercoating cracked over time an the water is dumped on and trapped inside the weldment. I have never seen this degree of corrosion underneath when the rest of the body is so good. I guess that this will be about a $700 repair to have it done right. There are four mounts for the sway bar frame. The front two look good. These are the back two. Just need to find someone. Here are a few pics....

1. Driver's side - seems to be the worst and the support is basically gone.


2. Driver's side - slightly different angle


3. Passenger's side - hole next to support

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I delivered Alarice to a gentleman to repair the rust. He had estimate a few hours and $100. Again I emphasized that I want it right not quick. I gave him $40 as earnest money. He thought that I could pick up Alarice Friday night. Friday comes and he calls me to tell me that after cutting away the rust the saw that the job was going to be more involved than he first thought. Actually, I was relieved to hear that because I was concerned that more was going to need to be done. HE said it would be done Saturday morning. I called Saturday about 1:00pm to check. He said that it is taking longer. Again, I was actually a bit relieved because I wanted it to be done right. 5pm he calls to say that it is done. I asked him how more more I owed him. I said $120. That would make the total $160. Still a fraction of what I excepted to get this done. I show up and give him $120. He stops and says that it is too much...the job is $120 total. I was surprised, but I believe that he felt bad because he gave me an estimate, then the job was about 3-4x more time involved than he first estimated. Here are some pics of the repair. OK it does not look like the car when it was new, but I am very pleased with the work that he did. I now have peace of mind that this issue is resolved. Now to do something about those body drain lines thatI am convinced caused this condition.

1. Driver's side -


2. Passenger's side -

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I suspected that this was primarily caused by the drain hoses. I confirmed this by spraying water on top of the car; the water ran right along the support tower. I need to come up with a longer hose and hose mount so that then water drains as low as possible.

I hope you do not have this problem on your W126, but please check....it is structural.

Thanks for the warning.

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Wow, those appear to actually be the track-rod subframe mounting points.
I bet if you had hit a curb pretty hard, the wheel could have pushed the track rod straight back and broken those rusty pieces right off!
The subframe bolt that attaches there is where I always set my jackstand when I crawl under the car - guess I better check my '91 out pretty closely.

Oh, on my Texas car I have found a lottle bit of rust in the following places:
- under the doors along the lower rubber weatherstrip.
- under the rubber strip on the firewall just behind the battery (acid fumes).
- a tiny spot on the roof just under the passenger door drip railing and behind the door upper weather stripping (sunroof drain).
- A tiny spot on the A-pillar (windshield frame) where one of the chrome molding screws attaches to the a-pillar.

I use the spray lube recommended here on the Forum (LPS3 I think) and give them a shot every month or so; seems to be controlling the rust pretty well. WD40 works pretty darn well also, kept my old Buick from crumbling down araound me for several years.

DG

That sub frame has four mounting points. The front two are perfect. The rear passenger was OK, but the structure right behind it was rusted. On the driver's side the plate that the frame mounts against was OK, but the support was gone.

I noticed the passenger's side when setting up the jack. There was a very small hole and I noticed some 'puckering' of the undercoating. At first it did not look bad........then I got a screw driver and my stomach began to sink. My first thought was that the driver's side would be much better. Oh, how wrong. To look at it you did not see the rust, but once I pushed on the undercoating the crumbling began.

I much say that I am pretty disappointed in Mercedes on this one. I have been under the rest of the car and it is great. Just this one area. Glad I found it when I did.

I just hope that everyone that has a W126 checks this out just to be sure.

It seems a lot is riding on the quality of the undercoating, since any breaks or cracks will let water in and then it can't get back out. I have been hitting the dry areas with either spray cans of undercoating or truck bed liner to seal it up a little.

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That's a nasty rust spot. From your photos, it looks like you could connect an extension hose, or plastic tube, where your hose makes a bend and then run it to the back of the wheel well. The W123 drains at the back of the well and thus has no water falling on anything but the road.

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I'm bumping this thread up because my car also has rust in these spots. I'm also going to have someone else fix it, and will post photos of the process when it happens.

-Jason

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I documented this issue in 2004.
Post #11 and #12.

Who has the most rust and still drives
Who has the most rust and still drives


NOTE:
I moved this thread to the "Body Repair and Restoration" forum.


Have a great day.

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