W126 560SEL, weird rust
 

I have an opportunity to buy a 560SEL, 1989 model 170K, black with gray leather, heated/power rear seat, a little rust on the left fender under the marker lamp. The weird thing is, the frame rails, just in front of the rear engine subframe mounts, are rusted enough that a pen will go right through. The rust is on both sides, in a very limited area. You can see the rusted area through the front wheel openings, behind the wheels. I'm wondering how common rust is in this spot, and is it fatal for the car? It just seems odd, given that the rest of the car looks pertty good.

the subframe
 

that you reference is a light guage metal structure that appears to gain its strength from its shape more than its mass. we often lift the cars by it although it is probably best not to. if lifted without any wood on the floor jack it can knock off t he undercoating and dent the member. this could easily lead to rust. i think if this is the only place you find rust that it may well be fairly easily repaired.

tom w

I couldn't tell by looking at it whether it is really load-bearing. The car has collision damage on the right front...smacked in the fender, damaged the upper and lower control arms and knuckle, wheel has cosmetic damage and the tire looks OK. I can get the car for several hundred dollars and I work in a bodyshop so repairs are not a huge expense, but the rust underneath alarmed me. My 420SEL is rust-free in this spot, thank God. Anyway, if it's a huge issue, I want to discover the scope of it while it is still someone's problem.

well
 

i would look and try to see why it is rusted. and if it is not too extensive i would patch it. if it isnt too big. i prob would just spray in the tube some rust binder and then patch the hole so that stuff wont build up in there. even a metal patch with roofing cement and sheet metal screws every inch or so.

if it is more extensive it might be necessary to weld the patch. i would make a pattern from cardboard and get a sheet metal shop to bend up a patch from the heaviest it can bend which is prob a little less than 1/8". then weld or again screw if not too big. welding is best but with all that undercoating and such fire is a danger. then of course prime and paint and undercoat.

tom w

Like Tom said, see how bad it is and what may have caused the rust. Is it a northern car? If so, check for rust on other areas of the undercarriage. If not, something obviously rubbed the undercoating off of that area, causing the rust, because the 86-91 W126 is supposed to be even less prone to rust than the 81-85 W126 models.

Good luck!

right
 

the only place i have seen rust consistantly in the 126 is between the plastic bumper thingee and the metal right behind the rear wheels.

tom w

Try to determine whether its a load bearing structure. If it is, I would avoid the car. Otherwise I would get it and patch the area to prevent further rot. Mine has rust holes in the frame inside the rear wheel wells behind the tire. Those were patched and it doesn't affect the car in any way.

Yes that is a very common spot for W126's to rust and yes it is structual. In my book once those rails are soft the car is a beater or parts car at best.

Also if those are rotted out their is more rust under their. Start looking for cracks in the udnercoating and peel it back.

Dont touch the car! A freind of mines had rust there and had to be taken off the road.

whoooah
 

let him check to see how extensive it is before condemning the car. it could be a small place caused by jacking it up carelessly and confined to a small repairable area.

tom w

It really looks like it's localized, the rest of the car looks solid, although I haven't had it on a lift yet. If I do get the car, I want a proper repair, but I'll be dipped if I'm going to buy 2 complete frame rail sections just to section them for this small area. For that matter, I have to imagine the drivetrain and interior would have to be R&I'd to avoid fire due to welding heat. Am I imagining things, or is this a bad idea?

if the hole is not too big
 

i would think welding is not nec. try to get pics and post for us to look at.

tom w