i am sure more than a few of you have experienced this: after the power window reaches its topmost position it goes thump, thump, thump,thump, thump as long as the button is held down. i have experienced this on my aunts 91 560 sel as well as my 300d so i know there is something fundimentally wrong in the gnarly MB window regulator design. can any identify what this noise is and how to rectify it? i suspect the stop pad but i could be wrong!

It is the window regulator. When you pull it out you will see the "teeth" on the regulator "rack" gear ground down at the ends. The thump - thump sound is the pinion gear on the window drive motor turning against those teeth on the regulator "rack" when it reaches the top. In addition, there was some distortion which, I figure exacerbated the condition. The rear ones in my 300D have been making the noise since I purchased it and that is what I found when I disassembles it one day. The regulators are close to $100/each. I will replace them when the windows will not close anymore, otherwise I just release the button when they are closed.

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Jim

As a preventative measure, it was recommended to me that on all of my Benz's, I watch the window, and stop pressing the button as soon as I figure the window is closed. Any extra time spent on the button puts pressure on the thin metal regulator, and eventually bends it over time ( besides wearing down the teeth ). Trying to bend the regulators back to shape is apparently out of the question due to the type of metal used. ( bummer ).

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It is a truism that almost any sect, cult, or religion will legislate its creed into law if it acquires the political power to do so. Robert A. Heinlein


09 Jetta TDI
1985 300D

My experience with my 1980 300D showed that the thump thump thump was caused by the gear slipping at top of the regulator's travel because the regulator frame had cracked and misaligned the gears. The cracking is an age related problem. The newer regultor replacements shouldn't have the same problem because they'll never see another 20 years and the castings are a little better.

HTH,

someguyfromMaryland

Is is possible that the "thump, thump, thump" is that plastic window slider is broken?

I had the exact same problem, and lived with it for a year or so, and then finally got around to replacing the regulator. In my case the teeth on the regulator were ground almost completely down. I didn't see any sign of cracking of the regulato mechanism, but it does flex some when you keep holding the switch button down at the top of travel. In fact, the flexing was starting to tear the door sheet metal at one of the regulator mounting bolt locations. To reinforce it I added some large washers.

The good news is that the teeth on the motor pinion gear are of a more robust material, and stay good. The regulator is a lot cheaper than the motor. It is a bit of a pain to do the replacement, but when you are done you'll wonder (like I did) why I lived with the "thump-thump-thump" for so long. The only other thing I vaguely remember is that I ended up having to cut the electrical connection (wires) to the motor. I can't recall if I absolutely had to do this, or if it just made it easier to get things out of the door. But it wasn't too bad reconnecting the cut wires afterward. I soldered them, rather than just using wire caps.

...with all the engineering they did with our cars, they couldn't figure out that our wives/children would just lay on the switch until they destroyed the regulator?

I have wondered if there is/was some kind of "limiter" built in to prevent this kind of damage - as I am on my 4th replacement window switch on my SL (they stick and the internal spring doesn't pop them back very fast, if at all), I am paranoid/careful about window travel.

I don't remember the same problem on any of the US cars I've been involved with...?

Hope to hear from Strife on this one..

Kevin

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"Dangerous with a wrench...and not smart enough to know it"

Stable (in order of acqusition):
'84 500SL, 280SEL (Euros)
'77 280SE. '90 560SEL
'79 450SEL 6.9,
'95 C280 (totalled by daughter 8/07)
'81 280SL (rescued) '88 300CE
'86 560SEC '95 C36
'01 CL55

DD's: '04 S500 4Matic (SWMBO)
'04 F150 Crew

No, there is no limiter on the power window mechanism, at least not on older cars that don't have a "one touch" driver window. Even though older M-B's are over-engineered in many areas, there are a few things that are under-engineered. Window regulators are one of these, in my opinion, especially the little teflon sliders in the window tracks (which are the other common failure mode of the power windows).

One of the features I really like about my daughter's VW Jetta is that the power window for the driver is "one touch" for both the up and down direction. (Plus it has that neat feature where the driver can turn the key in the outer door lock to drop all of the windows a bit, to allow air flow on hot summer days.)

Hi I just wanted to confirm something. I have a problem with my front passenger window similar to the above. It goes down, but on the way up it "thumps" and I need to pull it up an inch or two. Then it'll travel a few more inches and "thump" again. Repeat process and finally tell the passenger to stop opening the window!

So This is the current issue. Is it the same problem as above? Can I grab the rear window parts and use them to fix it (it's been wired not to run by the previous owner so they could fix the front driver window).

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1980 300D 300K KM - parting out
1979 300D 375K KM - parting out
2 300Ds for sale

The "thumping" sound when the window goes up is due to the teeth on the widow regulator being worn down. The front regulators are very different from the rear-window regulators, so you can't cannabilize parts. (If the window motor is running, but the window isn't moving at all, and there is NO thumping, then the problem is probably due to a broken/cracked teflon slider. These teflon sliders ARE the same at all windows, but they are riveted onto the regulator, so you still can't cannabilize parts.) In any case, if you are hearing the thumping sound, then the problem is almost certainly worn regulator teeth.

You need to get the specific front-passenger regulator. You don't need the motor assembly though. The motor's are pretty robust, and the pinion gear on the motor is also a harder metal, so its teeth don't wear down.

For some models there were multiple vendors of motors and regulators, with different numbers of teeth on the regulator. So you need to be a little careful in ordering the right regulator for your year and model.