Sunroof Greasing Technique
 

Got actual MB grease.

My understanding is that, after cleaning the rails, the trick is to use as little of that grease as possible. So I applied what I thought was a VERY thin coating. Seemed to operate smoothly...squeaks were gone. But then I noticed it seemed to be "catching" at a couple of points. So I wiped the rails with a paper towel, assuming that an even thinner layer would remain.

Does that sound about right? Can anyone help me quantify how much grease to use?

Thanks.

And now, again, it appears to be sticking. What am I doing wrong? What do I need to do?

I don't think having too much grease would cause a problem with the operation of the roof. If your roof has been dry and squeaking, it might have damaged or worn out slides (jaws) which are felt coated rubber/plastic.
Not too big of a job to remove the sunroof and inspect/replace them if you have the service manual. Bolt head locations should be marked with a paint pen before you remove them so you can get the adjustments back to original.

But why would I develop the problem AFTER applying the grease?

Those rubber sliding jaws would quickly get damaged if the sunroof was dry and squeaking. Some might even be missing as they can get ripped off their mount from the friction.
Not sure why it would start sticking after applying lube.

You just need to clean it well again and regrease. You may have to experiment with the right amount of grease. The only reason not to use too much is that it will attract dirt. Learn how much it needs for proper operation, then clean and regrease annually or more often if necessary.

Any recommendations as to what kind of a solvent to use? When I cleaned it first time around, I didn't use any kind of solvent...maybe that's needed to do a thorough job.

Are you sure it's catching or do you need to reprogram it. Try holding the button 10-15 seconds after its fully closed...then open it while hold the button 10-15 seconds after it is fully opened.

Wipe away the excess with a paper towel, then I'm sure brake cleaner would work well. If you don't have that, a mix of isopropyl alcohol and water would work fine as well.

Can I use WD40 instead of grease? Thanks!

Never use WD40 on ANY plastic bushing! It dissolves the plastic and creates a worse problem.

Use the grease or a heavy silicone spray. Light silicone (one which simply puts a "sheen" on the surface) lasts about as long as a fart in a windstorm.

Some of my friends swear by INOX for lubing plastic/nylon/teflon slides but I haven't used it enough to recommend it.

Thanks Mike, without your advice I'd have had some serious problems.