Aww crap - leaky sunroof

[flutes]

Breakthrough.

The rear left drain was clogged (not rusted) ... here's the long version of the story.

This was one of those rare days in Mercedes maintenance when everything goes better than planned.

Pouring water down sunroof channels it was evident that it was pooling in the rear left - the front drains were flowing out smoothly, the rear left not at all.

Using various guides I removed the sunroof (this took me bloody ages to figure out what the manual was talking about when it says "unscrew locking screw (16)".  Mine looks nothing like the manual and is a bolt.  This was the only frustrating part of the day.

The sunroof came out without any problems, and I was doing this by myself.  One other thing I realised today - my sunroof has always bee a bit "sticky".  This seems to be caused by the headlining - without the headlining in place the sunroof runs perfectly.

So sunroof out and I was still no closer to clearing the back left drain - I just couldn't get down there and couldn't really see what was going on, aside that there weren't any obvious blockages, and there wasn't really any rust I could see.

Next step I removed the blue trim that runs under the roof down the left side - I don't know what it's called properly so I'll call it the cornice.  Had to remove the sun visor, safety handles and struggle with this piece to figure out which way the clips holding it on came off.  For future reference, it slides towards the front of the car -the are three clips over the C pillar.  With this removed, and unclipping a small amount of headlining I had access to the hoses coming out of the sunroof drains from the underside - both front and back are in suspiciously good condition.  The good news here is that the sunroof frame is not rusted at all.

So thinking must be a blockage somewhere in the hose/channel I tried to find the end of the hose - I figured I could use the trimmer line up the hose trick to clear any blockage.  Everyone I've asked about this has said that the rear hoses drain into the rear wheel arch - well, not mine.

Mine drain into the cavity in the C pillar that is covered by a piece of brightwork.  I was able to see the end very easily, and work a piece of trimmer line up there to clear the blockage (problem 1 solved).

This setup is of some concern to me, as it seems like it may be the result of a not-to-original-spec repair job as the hose appears to be partially sprayed with grey paint.  I'm not sure about this though - can anyone comment?  Both left and right are the same.  This is a pic of the C pillar with the trimmer line sticking out of the end of the hose:



So here was success #2 - after washing there has often been a small amount of water around the inside rear RHS sill and I could never figure out how it was getting there.  I now know - the water was draining out of the sunroof channel, running down the rear hose, coming out the area you see in the pic above and then running around the inside of the door into the cabin.  The waterproofing on the back of the brightwork had deteriorated a long time ago.  To remedy this I put some cheap weatherstripping seal on from Bunnings.  Certainly not to spec (supposed to be for household windows) but it does the job OK and at 5pm on a Saturday afternoon I didn't have many options.

So with the drain unplugged and brightwork back on with new waterproofing I started putting the blue cornice trim piece back (sunroof was still off at this point).  This took a while - I just could not get all three clips in the C pillar back in - I think you need three hands to do this properly.  But the good news here (and success # 3) is that this piece of trim is now in a better position that it was before - the edges line up nearly perfectly and I was able to get the various seals between the frame and trim (looks like blue canvas over plastic cord) lined up and properly positioned, which they weren't before.  Gave the overhead handles a polish on the metal bits and cleaned the vinyl and they're back in looking good.  I was extremely happy with all of this, as usually if you don't know what you're doing getting trim back on can be a nightmare and look crappy.

Last thing was to put the sunroof back on to seal the car for the night (open garage so I can't leave things out or open).  The sunroof has a little but of surface rust around the bottom edges, but this will clean up easily and be treated with Miracle Paint.  With the sunroof out tomorrow I'm also going to give it a coating on the underside of Dynamat, just for good measure.  I'm actually a bit shocked there's no insulation under there - dark cars must let a lot of heat through there in hot days.

I'm pretty confident that I'll be able to sort the issues with the headlining dragging on the sunroof guides - I think this is just an adjustment, then my sunroof will be working as well as could be expected.  The lubrication on it is good and doesn't need attention.

That's it - long post.  With luck, the car will be waterproof after this and I can clean up the other side of the floorpans and put the rest of the Dynamat down.  My other pack arrived last week so I'm putting it over the rear seat, firewall etc.  Everywhere I can get to without console removal basically.

Now, it's time for a glass or two of red.

Cheers,
Matt.

[KenM]

Sounds like a pretty enjoyable day Matt, it also sounds like you're right when you say that it's a bit sus that the drain hoses end half way up your C pillar and have paint on them, could you not have tried to put in an extension piece or re-run the hoses altogether while you were in there so that they do drain all the way outside the car? I haven't had mine apart to that extent so may be showing my ignorance there. The sunroof lining does drag and cause quite a bit of resistance, maybe a spray with, (ahem) silicone could help out here?

Cheers,

Ken

[TJ 450]

Brilliant work!

I'm pretty sure the grey paint is the seam sealant/PVC material that is normally in that area... I know I've looked at it in the past and questioned its originality, but it's consistent between cars.

I have never been impressed with that C-Pillar drainage/vent system... a lot of garbage collects in there.

Tim

[flutes]

Ken, since that's original, there's nothing that could be done to improve that design without cutting through metal, something I wouldn't do!  It really is a pretty poorly thought out area.  Good to know that grey paint is standard, I was starting to get worried the had been some major repair work in the area that I wasn't aware of!

Ken the sunroof headlining seems to slide on felt strips each side that look pretty worn.  I'm not sure silicon would be the best lubricant, but I'll give graphite powder a go first.  That's also another area I'm not impressed with MB engineering - just to have the headlining secured by a handful of clips only at the front seems deficient.  It looks like an afterthought.

[flutes]

Report on yesterday's activities:

Pulled the sunroof out again, removed all of the guides from it so I could treat the rust and put Dynamat down.  Lubricated the rear seal with Vaseline).  There was a small amount of surface rust on the sunroof frame just in front of the rails, I scraped this off and painted it also.  The headlining panel was cleaned with Jiff (worked OK) and bent back into shape.  This was the biggest issue with the headlining dragging - the rear frame was bent in the middle so that it noticeably curved down at either side.  This was causing too much friction, slowing the sunroof.  So that is fixed.

Getting the whole thing back together again was something of a challenge.  I'd unbolted all the guides from the sunroof and didn't know exactly how they should be positioned for best operation.  There was a lot of trial and error once it was back in place and a few stuff ups/re-dos.  It still feels like the left hand side is dragging but it was about the best I could get it.  I've seen a guide on adjusting the height, but nothing about how to best adjust the guides/rails for smooth operation.  If anyone has one it would be appreciated if you could send it...

Lastly, I used a stupid amount of graphite powder on the edging strips of the headlining.  (I didn't intend on using so much, that stuff just goes everywhere.)  This really helps it slide smoothly, and with the clips repositioned and pushed in properly (they weren't before) and the bend in the rear frame removed it's now running pretty well, if not a little stiff still.  It still feels like there is some stress in the system that I haven't identified yet.

So now in theory the car is "waterproof".   I wasn't prepared to put this to the test today - it was bucketing down in Sydney this morning and I've always found the freeway in peak hour traffic top be a pretty poor place to stop and debug any leaks if anything is still wrong!