Hi all,

Last fall, my sunroof made a sickening noise when I went to pop it
open one day. I managed to get it closed, and left it alone until I
had time to work on it, which was last week. One of the angular
lifting arms, which are the fancy mechanical pieces that allow the
sunroof to both slide open AND pop upward, had broken. And when I took
things apart, the other one broke during disassembly! I had heard all
the stories about how this is not a DIY job, and is best left to the
dealer for $1000+ in parts & labor. But, being the tightwad that I am,
I figured I'd try it myself first... and if I screwed it up, I'd have
to let the dealer fix it.

The worst part is getting the sunroof disassembled with it broken.
Normally, the first step in disassembly is to open the roof fully,
then remove the liner and front rails. Well, that is not possible when
the mechanism has broken. (See below for tips on how I did it in my
case.) After getting the trim panel out of the way, I could see the
nuts that were to be removed. I scribed marks around these so I could
re-assemble in the same position later. With the metal roof removed,
the hard part is over, then it's just a matter of carefully following
the factory service manual procedure - which, I must say, is a little
vague in some areas. I also marked exactly where the lift arms attach
to the "transport bridge", the wide section that the sunroof cable
attaches to.

Once the lift arms, drip rail, and bridge are removed, you need to
clean everything up and then re-assemble. The procedure said to lube
moving parts of the lift arms with Gleitpaste (special sunroof lube),
which I did. It also said to lube the rails, and the felt pads on the
lift arms, which seemed weird but I did it anyway. It looked to me
like the felt pads would be fine with no lube, but oh well.
Installation was relatively straightforward. I had the pliers to pull
the metal roof forward, but I really don't think they're necessary.
The small plastic gauges are needed, and come in handy, but it took
some head-scratching to figure out where they attach. I forgot to take
a photo of them in place - wooops. When putting things back together,
I used the marks I had made when taking things apart, and it turned
out quite well - I didn't feel the need to do further alignment, it
looks fine. And it works perfectly! I was a pretty happy camper by
this point. :)

If you are just taking the roof apart to clean it, the only nuts that
need to be removed are the 2 on each side with the wide washers that
attach the metal roof to the bracket on the lift arms. There's no
adjustment here, no need to mark them, AFAICT. It's the two small
screws on the side that attach the bracket to the lift arms that allow
vertical adjustment for the rear of the roof - leave those alone
unless you're replacing broken arms. The other important ones are the
6 screws that attach the arms to the transport bridge. Mark the
position of the arms on the bridge - I just scribed a line along the
edge. This is less critical, IMO. Don't mess with the nuts on the
front of the metal roof panel.

The EPC indicates that the old lift arms have been superceded by new
improved lift arms for early VIN numbers only - the break is the
mid-1987 model year, and of course I had the early style. In my case,
I needed both sides (at $100+ each), plus a new drip rail, new metal
guide rails, and - allegedly - a new cable. However, you don't mess
with the cable at all. The cable design was also changed, and the EPC
says the old part "must no longer be installed". I'm guessing that MB
figures if you're doing major sunroof work, this would be a good time
to upgrade the cable too. However, it's not *required*. I already had
the new cable, and figured I might as well go for it. It takes quite a
bit of force to remove once it's run out of the motor, and kind of
"jerks" out in sections - it seems to hang up periodically. Installing
the new cable was awful - I almost thought I was not going to get it
back in. With a friend helping to twist the cable, and me pushing, we
finally got it back to the motor and it pulled the rest of the way in
normally once it hit the motor drive gear.

Disassembly tips:
This worked on my car, but I can't say it will always work - I don't
know what the usual failure mode is:

1) You have to get the liner/trim panel off the sunroof. There are 4
plastic press-in clips near the front that must be popped downward. I
was able to partially raise my sunroof, and pried it up by hand as
best I could, propping it in position with whatever won't scratch the
paint. Then, through the maybe 2-inch opening, I could shine a
flashlight in to see above the liner panel. I used a long (24-30
inch), flat (3/4" wide by 1/16" thick) metal bar to wedge in between
the metal roof, and the metal frame of the liner panel. This is VERY
HARD to do unless you can look at another 124 with a good sunroof, and
pop the liner down (with the sunroof opened) to see how the clips
attach! Otherwise you can end up prying between the wrong pieces, like
I did, almost damaging the very expensive trim panel. Once I figured
out where to pry, I got the panel popped free, and could then slide it
backwards and see the bolts on the underside.

2) With the liner out of the way, you can remove the two nuts with
attached, wide washers. This allows the rear of the roof panel to pop
pretty far upward. However, the front is still hooked under the rails.
Remember, normal disassembly specifies to open the roof, *unscrew the
rails*, then close the roof. With the rails out of the way, the roof
simply lifts off with the 4 rear nuts gone. But not in my case. Since
the roof is now separated from the lift mechanism, I lifted the rear
up and manually pulled the roof back. It only moves a couple inches,
but that's all you need to reveal the front guide rail screw. Remove
the screw (both sides), push roof back forward. Lift the roof upward
and prop it up with something that won't damage the paint. You can see
the remaining 4 rail screws on each side. A small, flat, ratcheting
screwdriver is what I used to fit in the very limited space to get the
screws out. With those removed, the whole metal roof now lifts off the
car, and the guide rails are also removed. The rest of the job follows
the factory procedure.

Anyway, in summary, it wasn't nearly as bad as I thought it would be.
And, I had no major alignment issues afterwards. Between using the
plastic guide tools, and marking the bolts, it was quite painless. If
your 124 roof is starting to act up, and you plan to keep the car long
term, I'd almost consider proactively replacing the lift arms (and
other parts) BEFORE they break. It will be a far easier job if you can
still open & close the roof - trust me. The cost of parts are,
roughly, $100 each for the arms, $70 for the new style drip rail, and
$15/pair for the new style rails. The new cable isn't needed, but will
be $60 or so if you want to do that too. Prices are based on current
wholesale, Dec-2005, and of course are subject to change, etc. If your
car is after VIN #A354333 (for sedans), you probably don't need all
those parts, just the lift arms, which appear to be the
fragile/stressed item.

I'd almost say it's not that bad of a job to fully disassemble a
working sunroof, for a proper cleaning (note all the greasy crud on
the old arms in my photos), lube, and re-assembly. Just don't force
anything - it all comes apart without major effort (except the sunroof
cable replacement, which I would avoid if possible.)

Photos are here:

If I ever do this again, there are a couple things I'd like to add
photos of, like what the plastic install guides look like when
inserted, etc.


Best regards,

Dave M.
Boise, ID
1994 E500 - 95kmi  (Q-ship)
1987 300D - 261kmi (Sportline)

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