Notes for DIY - W124 monowiper/ACC blower access - PeachParts Mercedes-Benz Forum

Jeremy5848 · #1 10-17-2009, 01:27 AM

My 175 mile drive to Monterey a few days ago was done in continuous rain. There were cars and trucks off of the road all over -- the idiots just won't slow down. After almost 4 hours of use, the monowiper of my 1987 300D Turbo (W124, OM603) began to squeak. Not a continuous squeal, just at one point in the cycle, as the blade began to return from right to left. I figured I had a dry bearing somewhere.

Fortunately, the drive home was mostly rain-free and the squeak got no worse. Today I pulled off all of the panels covering the monowiper (I've never done it before) and learned a few things. The punch line is that the squeak was caused by one of the four bolts that holds the monowiper in the car. It had started to back out of its hole, perhaps insufficiently tightened by a previous mechanic, and was rubbing each time the mechanism rotated the drive arm across it. In the below picture, you can see the shiny head of the bolt. Tightening the bolt eliminated the squeak.

Getting at the wiper assembly was made more difficult by section 83-140 "Grille on air inlet removal and installation" in the FSM (CD-ROM version) because the factory's pictures didn't match my early (build date July 1986) 1987 model year car. Some of the parts in 83-140 aren't even in my car. There are some good DIY instructions on this and other forums, particularly the write-up by the Australian Anthony Tugwell, even though it featured a 1989 RHD gasser. Removal of these plastic "partitions" is necessary to access and remove the monowiper and then to get at the ACC blower, which is underneath the monowiper. Most 124 owners will have to do this job sooner or later. It is relatively simple once you know how but it is time-consuming and therefore expensive to pay a mechanic so you might as well learn how and do the job yourself.

I photographed as I worked and here present my findings in the hope that someone else may be helped by my adventures. I'm not going to repeat all of the instructions that the other DIYs have thoroughly covered but instead will cover problem areas that I struggled through, figuring that others may also need a little extra assistance. Note that "left" means the left (driver's) side of the car. Warning: these notes are not necessarily in the order that you use to remove the various parts and pieces! Also, my information may not completely apply to your car. Finally, I noticed that the parts in my car didn't all agree with the part numbers in EPC. Perhaps a PO had to do some substituting.

One of the challenges was that the various DIYs give different numbers of fasteners for various pieces of the puzzle. It's very hard to find five screws if the part in your car uses only four screws, for example. Below is a picture of the "partition panel" (124 620 13 78 according to EPC but the part in my car was 124 620 09 78). I call it the "big partition" because it's the largest one. It's attached with 4 screws at the top and 2 screws at the bottom; some instructions say 3 screws at the bottom. Also note the captive nuts for the 2 plastic screws that hold the insulation panel to the partition. There are also two outer plastic screws but in my car these did not have to be removed. The 2nd and 3rd following pictures show the plastic screws in place. In my car, the screws are captive in the insulation and don't need to be removed, just unscrewed. The plastic screw on the left (driver's) side is hard to get at as it is behind some wires. After loosening the plastic screws, pull the insulation forward to see the two front screws that attach the "big partition."

With the insulation pulled forward, you can see the two Phillips head screws. I used a magnet to capture the screws so I didn't drop them into the bowels of the engine.

In my car there is a "partition panel, top central." It is in EPC (124 620 07 78) but it is not in the FSM and it does not have a part number molded into it. This panel is attached to the "big partition" and to the forward firewall with two clips (001 988 76 78) on each side. One of my clips was missing. You have to remove the two rubber mouldings that cross the engine compartment to see and remove these clips. Be careful not to drop them as they are very small and easy to lose.

The left and right rain gutters are attached by a white plastic clip at the inside end. To remove, pull the clip forward with your fingers or a pair of pliers. Being plastic, the clip is fragile, as other writers have mentioned. One of mine turned out to be missing. The part number of this "connector" is 124 628 02 28.

As you're putting the "big partition" back, note that the rubber seal that surrounds the wiper head goes over the partition and the c-ring goes on top of that, held on by its 4 screws. This order of parts is critical to everything fitting together and being water-tight.

I hope this helps someone. Let me know if you need to see other pictures, I have more.

pawoSD · #2 10-17-2009, 10:38 AM

Thanks! This is very helpful. I'm still hoping I don't need to remove mine any time soon....

BrianCostello · #3 10-18-2009, 08:16 PM

Talk about timing!

My wiper stopped on me today. I pulled over, checked the fused (they were fine) upon re-starting the car the wiper worked. But it seemed slower and had a noise similar to what you described.

I will take it apart and tighten things up. I will also lubricate any moving parts. any suggestions???

Thanks for the write up.

Brian

Jeremy5848 · #4 10-18-2009, 08:27 PM

Quote:

Originally Posted by BrianCostello

Talk about timing!

My wiper stopped on me today. I pulled over, checked the fused (they were fine) upon re-starting the car the wiper worked. But it seemed slower and had a noise similar to what you described.

I will take it apart and tighten things up. I will also lubricate any moving parts. any suggestions???

Thanks for the write up.

Brian

If you remove the four bolts, the whole wiper assembly will come out (watch the electrical cable!). Then you can look it over and lubricate anything that looks like it needs lubricating. I have not had to do that yet but there are threads on this forum that talk about taking the wiper assembly apart and they should give you the information you need.

Jeremy

Deezl · #5 10-18-2009, 08:57 PM

Excellent writeup! Thanks for your effort and time.

sasquatchgeoff · #6 10-18-2009, 09:59 PM

Fantastic addition to the DIY. It seems the FSM's, Haynes, Alldata, etc are always gasser-centric (several aspects of the diesel firewalls ARE different) for this complicated procedure and we "D" people have to fend for ourselves. That is certainly made easier with write-ups like this. THANKS!
BTW - I just finished replacing the blower in my 201, not quite as complicated as the 124, but generally the same with a few less plastic parts. Also, its a great time to clean the goop out of the windscreen gasket and surrounding mouldings, and vacuum the birds' and rats' nests out of the cavity covered by the big "grill" partition panel.

a2t · #7 10-18-2009, 10:18 PM

Excellent write up. I went thru this exact stuff on my 87 300D when I was replacing the blower and resistor. I thought I was going crazy finding all the differences in the FSM to my car...

Go a few layers deeper into the onion and replace the blower motor while you are at it. Once all that stuff is removed its not very difficult unless you keep the squirrel cages and have to put them back on the new motor shafts. Those things have to be aligned to like .050" !

All hail the monowiper. I will sadly miss that thing when I finally sell off the 300D and switch to the SDL. Just another 1 of the many things MB got completely RIGHT with the 124. That motor and linkage is so powerful you can actually feel the car move a bit at a stop light with it going full blast. The SDL wipers are no comparison

babymog · #8 10-18-2009, 10:20 PM

I like the way it THROWS the water from the windshield, on low, doesn't slide the water along but throws it sideways. Nice.

Jeremy5848 · #9 10-19-2009, 01:02 AM

Quote:

Originally Posted by babymog

I like the way it THROWS the water from the windshield, on low, doesn't slide the water along but throws it sideways. Nice.

As long as you don't decide to wash the windshield while stopped in traffic alongside a rumble of Hell's Angels.

babymog · #10 10-19-2009, 10:36 AM

I keep a Harley-Davidson badge in my trunk for a peace-offering.

#11 10-19-2009, 10:42 AM

Quote:

Originally Posted by Jeremy5848

As long as you don't decide to wash the windshield while stopped in traffic alongside a rumble of Hell's Angels.

Don't worry, their bikes will break down before they catch you.

#12 10-19-2009, 11:00 AM

Nice photo instructions.

Just for the record though, any time you go to the wiper mechanism, unless it has been done recently, go ahead and slip it apart and grease the slide mechanism. Use a good lithium grease. This is even more important in cold climates.

Jeremy5848 · #13 10-19-2009, 11:51 AM

Good point. In fact, I did adjust the mechanism until the slide was sticking out as far as it would go. Then I put Mercedes sunroof grease on it. I figured that a waterproof grease that wouldn't attract dirt would be good for the wiper too.

#14 10-20-2009, 11:00 AM

Yes, that should work well. It should stay in place. That's the key.