Sound of plastic snapping while closing sunroof - PeachParts Mercedes-Benz Forum

beaulieub · #1 08-20-2006, 07:55 PM

'80 300SD. Was closing the sunroof yesterday just before a majhor rainstorm and heard a large snap sound from the sunroof. This was followed by the roof siezing and a loud clicking noise coming from the trunk. Roof had maybe another 2 inches to close. After trying reverse - forward, etc. a few times, I was able to pull the roof closed while the motor kept clicking in the trunk. Haven't been able to check this problem yet cause its still raining and will be tomorrow too. Got any ideas what plastic would crack up in the roof? Searched the archives and cant find this exact problem. Can anyone suggest something?

Thanks Bert - NH

t walgamuth · #2 08-20-2006, 08:03 PM

the sunroof is pulled back and forth by cables on pulleys. i have never seen them but it wouldnt be too surprising if the pulleys are plastic. so if you broke a pulley that would prob cause it to not work. and a slipping sound in the trunk where the motor is.

the only other thing is the air deflector. they typically get lazy when the car gets a bit old. cleaning and lubing everything will go a long way toward keeping these old sunroofs working.

tom w

dannym · #3 08-20-2006, 08:09 PM

Maybe the cable snapped?
I doubt your going to find out what broke without taking it apart. This link should help you:
http://www.diymbrepair.com/Sunroof/

Were you able to crank it manually from the trunk?

Danny

JimSmith · #4 08-20-2006, 09:31 PM

Sunroof repair is not always easy. First, what kind of sunroof do you have, a simple one that just retracts, or one that does the lifting of the rear edge, and retracting?

The clicking is not a bad sound, just the clutch on the drive motor letting go when the torque gets high enough and the cable doesn't move. The rest of this is from memory and I am getting old, so my memory isn't that sharp - in other words, when you get in there and things are slightly different, I don't want to debate anyone about these details. The system on the simple sunroofs operates with a cable that comes out of a steel tube just behind the opening in the roof for the retracting panel. The tube has a slot in it at the 12 O'Clock position, and a fitting that grabs the end of the cable, then extends through this slot and has little delta wing like protrusions with holes for screws to fit into the actuating bar on the sliding panel. As the sunroof retracts this cable is just pulled down the tube and roof follows. The "actuator bar" it is attached to is a lever that first unlocks and lowers the panel when it opens and then, when it shuts the last few inches of cable travel raise the roof panel and lock it into position.

The first step is to get the interior liner off the sunroof panel. This part, on the cars I have worked on with just the retracting feature, is held to the forward inside edge of the moving panel with those MB metal spring clips. I used a knife and pried the first one off and then used my fingers to get the rest off. If the roof is stuck closed, as mine was, you have to bow the headliner panel once it is free and pull it into the interior. The front edge has metal frame parts and it will bow, but be careful. If you can open the roof, open it about half way or less and them pull it out the top (the roof openning is larger than the sliding panel, and the headliner, so it comes out easier that way). Once the headliner is out of the way, you will need a flashlight, but the rest of the stuff is obvious. The cable and tube, the connection and the lever/actuator arm and its connections. That is likely where the problems lie.

On my car the little delta winged thing lost a screw and instead of coming to a stop in the closed position, the cable continued being played out, as the connection to the actuator lever was now a pivot and the cable wound around itself, and came out of the guide tube too far.

Simple fix for me, about $0.32 for a new delta wing connector and another few pennies for two new screws. Good luck, Jim

beaulieub · #5 08-20-2006, 09:47 PM

Good info - Thanks. My sunroof is the simple older style that only retracts. It isn't capable of raising the rear up for venting. Question about the hand crank. I did try the hand crank. I found the little adapter that fits into the motor assembly(?). Is there some other part that I'm missing? What turns the adapter? Am I supposed to put some pliers on it to get it to crank?

JimSmith · #6 08-20-2006, 11:46 PM

The hand crank is useful when the motor is not working. Your motor works so you won't do much more than the motor did. You should have a device in your tool kit that allows you to turn the drive nut from the motor shaft into the "transmission" which is a clutch device and set of gears to drive a worm and roller that pushes and pulls the cable. Jim

beaulieub · #7 08-21-2006, 10:40 AM

Ahhh! So I'm also missing the toolkit on this car. Thanks Jim, I'll have to search for one at the junkies.

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