How do I repair/replace this sheared bumper mount stud?
 

So while we were removing the potential replacement bumper for my 190E one of the four studs sheared off the bumper. At the time we thought it would be fairly simple to fix so we really didnt think anything of it however upon closer inspection...

It seems like it might be more involved. I was hoping that you fellows might have some ideas on the problem.

We initially were going to cut it off, drill it out and weld in a replacement bolt however it appears that the metal is aluminum.

I guess I could just talk to the body shop and see what they think about it since they're going to be the ones painting and installing it.

I'd much rather they paint/install this bumper over my current one as my current one is from a pre 1989 car and is the incorrect style for my model year.

http://i.imgur.com/IOg0Q96l.jpg
http://i.imgur.com/pqjusPNl.jpg
http://i.imgur.com/qJylP17l.jpg
http://i.imgur.com/3i9nwMHl.jpg
http://i.imgur.com/scuZelhl.jpg
http://i.imgur.com/PXLec4vl.jpg
http://i.imgur.com/XSfRkROl.jpg
http://i.imgur.com/ZENyPajl.jpg
http://i.imgur.com/XNJTlDbl.jpg

Can you access the inside of that mount with the bumper installed? If so maybe you can use a nut and bolt. The stud goes in to the mounting ear of the energy absorber, right? If so you could also try using a nut and bolt and attaching the energy absorber on that side, then install the energy absorber to the car instead of the other way around.

The bumper bar / bracket looks to be extruded aluminum.

Pic 4 shows the bracket to be riveted on so it will be somewhat of an ordeal to remove.

Look on the back of the bracket, are the studs single or paired to a strap? If single they are likely serrated ( like a press in wheel stud ) , in that case you can pound the stud out and possibly use one from the old bumper. If there isn't enough room to squeeze the new one in, you might be able to shorten it a bit. If the studs are paired up, you will need to cut the strap first or possibly extract the pair.

Another possibility ,if you don't have enough room for wrench, is to use a bolt from the car end and weld a strap to a nut on the bumper side. The strap on the nut will act as a permanent wrench.

Can that plate be removed from the bumper? If not, just grind the stud off, drill it and put a bolt in from behind. If there isn't enough room to slip the bolt in, slot the hole (side to side) and use a fender washer.

From what I can tell:

1) The plate IS aluminum. My magnet only stuck to the bolt stud itself.

2) They are single entities. Likely serrated as you suggest or pressed in somehow.

3) There does not appear to be enough room to access it with a wrench. Drilling and or cutting might be the only option.

I was thinking that it might be possible to cut the plate off the large assembly and re-work it off the bumper and then just bolt the plate back on.

However! The good news it the body shop said they would take care of it...I assume they are much more skilled than I am at this...

The only question that remains is, how should it be painted?

Traditional two tone, where most of it its the same color as the cladding and the bumper strip is black?

Or monotone, the same color as the cladding?

I would like to see how they remedied this.
What do your original paint colours read? Mercedes had some great looking paint from factory with shaded cladding.
The first impression I see with 2 colours is an added depth of wow.

The broken bolt could easily be drilled out then use a stud and nut it from the inside.
maybe that was said already anyway have you considered painting the car yourself.

Hm I think Id have to have it painted to whatever scheme the rear bumper is painted..other wise id have a mismatch or would have to pay to have the rear bumper painted to match.

The only 190's I've seen with monotone bumpers are the 16 valves. But the bumper style is different and looks more appropriate.

All the other 190's have the bumper matching the cladding and the impact strip black.

This was my first thought however there is no clearance for getting a bolt back in once the existing one is drilled out.

Painting it myself?

Have you removed all your cladding, There can be some big suprises.
I removed some of mine today.
The small piece behind the rear door On the front Rear quarter was difficult. I removed 6 today on 3 cars.
I found the top pulls straight out leaving the bottom in tact.
I pulled the top out slightly and sprayed 'simple green' to soften up the plastic.
I then use a hand held torch "plumbers" torch and applied heat briefly from a distance 2 times waiting in between.
One plastic piece about a quarter of a inch stays with the cladding, And the other plastic stays on the car.
Find the split between the two and use a large shank screw driver and pry straight apart, slowly.
This worked for me without any damage on the clips or cladding.
There are 4 , 1 in drains under the rocker cladding which most likely will require a wire brush and reprimer'ed.
A gallon of base coat or if you can get enamel is not expensive.

Edit: previous post.
The 4 , 1in drains are actually lift pad reinforcements which are 1 in round pipe approx. 5 in long.

Well the insurance company approved the used bumper and a new fender for the repairs. My dad dropped off the used fender to the body shop today and the car goes up Sunday.

I know that I've got some surface rust on my lift pad areas that I need to attend to. I think the lift pads got removed years and years ago and thats why there is any rust at all. My 300D has no rust in those areas.

I read here that that 201 and the 124 were the first MBs to use galvanized steel.

Galvanized is necessary saint.