126 coupe - window tightspots?

[Somebody]

So, my 500sec coupe seems to be having the reasonably common issue in older cars of window tight-spots.

You know, when the window mechanism gets to a certain position, the motor has to apply a lot more torque, and the window slows down, sometimes almost stopping. Once it gets past that position it's all fine again.

I had this a lot with pretty much every vintage car I owned, is usually down to bushes bearings or rollers becoming semi stuck through age/corrosion/lack of use, and usually putting penetrating fluid on the affected parts and working the window up and down a bit fixes that right away, and then some spray-grease on the affected parts keeps them good. Or worse case scenario is having to disassemble and clean and re-assemble the lifter mechanism.

But, unfortunately I have no idea about the layout of the mechanism in this car, since its my first Benz, and also the folks at Benz seems to have very kindly hidden the rear mechanisms in like THE most awkward hard to reach area, inside a double-skin in the rear side panel that's barely accessible.

So, this is where I need your help. Are there any seasoned Benz people here who have had this mechanism apart a million times and know it well?

ARE there any bushes or bearings or rollers that become susceptible to drying up and getting sticky and causing tight-spots in the mechanisms action?

And of so, could you roughly describe where they are at and how to reach them?

Generally any tips etc?

I know its nothing particularly complicated, but it would be cool to get some input from someone who did the job themselves.

Thanks

 

[Somebody]

Well, I think I managed it all by trial and error, and since nobody answered Im gonna share my experience in case it helps someone else out in the future.

The culprit seems to be the scissor-action type member that's part of the lift mechanism.

Most of the pivots and sliders in the mechanism are plastic on galvanized metal, so they are pretty much trouble free, since plastic does not corrode and galvanized metal does not corrode unless in a really harsh environment, so on mine they were fine.

However, there is one pivot point where two moving parts intersect, forming a scissor action kind of setup, and that pivot seems to be metal on metal, and therefore vulnerable to sticking, and THATS the culprit in this case got sticky with age, through tiny amount of internal corrosion and lubricant drying out probably.

The reason why it was causing a tight-spot is really common for any bush type setup which goes through a limited range of motion, obviously the previous owner only opened the windows up a little bit, so in that part of the motion it was free, but opening it all the way it got tight. Kind of like an old pair of pliers, if you understand that reference (people who do will instantly know what I mean).

I ended up taking everything apart because I didn't really have any info to work with, however now that I did, I figured out that it's actually much simpler. You can get to the offending bush by removing the rear quarter trim panel, loosening the fat-lazy-people-seatbelt-mechansim and then removing the bolts that hold the top cover/inner window wiper seal, and removing that. Then you get good access to the mechanism from the top, without having to remove the window, mess up window adjustment, or remove the mechanism. You can move the window up and down till its in a decent place (but make sure you guide it by hand, otherwise, without the inner wiper seal, it can jam against it's channel) until that scissor section pivot is accessible. I covered it in penetrating fluid, moved the window up and down a few times, more penetrating fluid, move it etc etc till the penetrating fluid flushed out all the crap out of that pivot and it stopped being stuck. Then I oiled it with GL4 manual transmission fluid (thats a really good substance for general purpose oiling of things!) while it's still wet with the penetrating fluid, because GL4 dissolves in penetrating fluid, and therefore gets wicked into the inside of the joint. Then put some spray grease on it just for good measure.

It took me a couple of hours and I ended up disassembling the whole mechanism and removing everything, but that's because I had no idea of the mechanisms layout or what the problem was or how everything worked, however using the method above I got it should take 20 mins max.

And my window works fine now!

Might as well cover the inside of the quarter panel in your favorite brand of liquid rust prevention fluid too, since that place is vulnerable to rust. Luckily mine wasn't, but as with any vintage car a liberal dose of anti rust treatment inside any panels whenever you have access to them anyways is a good idea.