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Sunroof Drain locations and hints on clearing them

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  • Sunroof Drain locations and hints on clearing them

    Many of our C4 100/S4s and A6/S6s (and B3s and B4s) were equipped with either steel or glass sunroofs which live in a sunroof "cassette" bolted to the roof of the vehicle. The sunroof seal is not perfect and some rain water and snow melt will seep past the seal, into the sunroof cassette. To manage that water and keep it from entering the car interior (and wetting and destroying the headliner), the sunroof cassette has four drains, two in the front that go down the "A" pillars to the front door hinge area and two in the rear that go down the "C" pillar and exit in the rear wheel well, behind the liner.

    These drains need to be kept clear so that they drain. Otherwise water can leak into the interior. Access to clean the drains is achieved by opening the sunroof all the way. Methods that have been used successfully clear the sunroof drains include weed-wacker nylon "string" (pushed down the tubes) and old speedometer cables. High pressure compressed air might be too much for the tubes. Canned air (like the stuff used to blow out computer key boards, etc. has been used).

    Here is a diagram of the location of the drain tubes and a photo of a sunroof cassette exposed after the headliner board was removed:




    Base photo courtesy of IrishS2 (Eric) on the S2Forum

    FRONT DRAINS (SEDAN AND AVANT)

    Here is a photo of the front left C4 sunroof drain exit point:



    Steve M says "The front drains exit in the front door jambs- they are difficult to get to, but rarely clog."

    REAR DRAINS

    SEDANS

    Here is a photo of the left rear C4 sedan runroof drain exit point (right side will be similar):



    Steve M says "Rear drain is just behind the rear wheel well, and are more likely to clog because of the rubber 'valve' similar to the one in the cowl area. You can get at them with the bumper installed, but they are a lot easier to see with it off."

    AVANT REAR DRAINS

    I couldn't find the rear drain on my S4 avant so I asked for photo help on the S2Forum and here. With the help of Marco from Montenegro(Majorcina on the S2Forum) and Doug W (islingtonaudi) and Mike A. from here, I got the photos that I needed.

    The factory diagram is not specific to the avant and is vague as to what happens. What I discovered from the photos below is the rear avant drain goes down inside the avant's "D" (rear most pillar),into the two storage cubbies, just past the avant rear corner taillights and into a grommet that is just to the rear of the cabin air vent. I just confirmed this on the V8 S4 avant. (Watch the sharp edges on the metal if you sick your hands in the cubbie holes - they will slice you good (don't ask))

    Left side (Majorcina was doing a repaint so he removed everything, even the sound deadening foam):


    Photo Courtesy of Majorcina on the S2Forum

    Right side:

    Photo courtesy of Majorcina on the S2Forum

    Here is the big view:


    Base photo courtesy of Majorcina on the S2Forum

    Here is islingtonaudi's right rear drain on his V8-converted 1997 A6 avant:


    Photo courtesy of Islingtonaudi on quatttroworld

    Here is Mike A's left rear drain:


    Photo courtesy of Mike A. on quattroworld

    Back to Majorcina, here he is with the left rear drain grommet pulled out of the body:


    Photo courtesy of Majorcina on the S2Forum

    None of these avant drain exits can be seen easily with the bumper on.

    Now that you know where the drain entrance and exit points are, there is no excuse to not periodically clean out them out to prevent water in the cabin and headliner fabrics from coming loose. (But that is another post - to come).
    RS2'd 93 UrS4 5 spd sedan
    94 UrS4 V8 6 spd manual avant

  • #2
    Very useful info.Thanks for posting.
    Regards
    Ryss
    www.autostart.co.za

    Comment


    • #3
      Still trying to resolve my leaking sunroof issues but need a bit of help. I'm pretty sure the rear drains are blocked so I've been looking for where they exit the car. I haven't got the rear bumper off but I'm fairly sure they're not in the same place on the S2 Avant as they are on the S4 Avant.

      Can anyone help please?

      Thanks

      Alistair

      Comment


      • #4
        A really important part in this scenario is the "drip tray" part 14/15 in the diagram above. This sits underneath the rear of the sliding panel, catches water dripping through and directs it into the cassette base so it can get to the drain tubes. This "tray" (it's actually like a long narrow bridge) is clipped to the back of the sliding mechanism and travels back out of the way when the roof is open. It can become disconnected from the sliding sunroof panel and get left down at the back of the cassette at which point you get a very wet headlining. If you move the sunroof into tilt position you can see if it is present and correct.

        S2 Coupe 3B Project


        Ur quattro restoration

        S2 Avant

        Boost is the new rock and roll!
        sigpic

        Comment


        • #5
          Drip tray is fine. I know about that one from experience.

          I ran some water in while the car was on a slope, Pointing down and and upslope. Fronts drain fine and can be seen running out on the floor. Rears show no sign of of draining. The result is that when you brake, the water all heads to the front. It can't drain quickly enough at the front so it sloshes over the top, wet head, legs etc.

          Tried dropping the sunroof cartridge a bit and feeding a cable into the top of the drain tube. It got stuck about 2ft down. Think this was mostly due to the dififcult angle of entry. So now I want to find the exit drain and try from the other end.

          Thanks

          Comment


          • #6
            Originally posted by Alistair E View Post
            .. So now I want to find the exit drain and try from the other end.Thanks
            This photo is of an S2 avant. The rear drains go down the "C" pillar so they have to exit either in front or behind the rear wheel. I suspect that they are the same as the C4 avants, behind the rear wheel. Look for the tubes as they pass through the rear corner cubbies.

            RS2'd 93 UrS4 5 spd sedan
            94 UrS4 V8 6 spd manual avant

            Comment


            • #7
              Looked at the photos of the C4 drains but can't see them in the same position. I'll have to have another look from underneath but I think they might be behind the arch trims.

              Would be great if someone had a definitive answer. Anyone?

              Comment


              • #8
                Originally posted by Alistair E View Post
                Looked at the photos of the C4 drains but can't see them in the same position. I'll have to have another look from underneath but I think they might be behind the arch trims. Would be great if someone had a definitive answer. Anyone?
                I asked IrishS2 (Eric the Mad) and this is what he said and provided (in his thread and copied here):

                Originally posted by irishs2 View Post
                Might not do you much good. As far as I remember the rear drain is inside the rear wheel arch. Which at this moment in time is covered by the liner.
                RS2'd 93 UrS4 5 spd sedan
                94 UrS4 V8 6 spd manual avant

                Comment


                • #9
                  I asked Eric (IrishS2) about the hose just by the rear tyre and this was his reply:

                  Originally posted by irishs2 View Post


                  Thats the filler cap drain.

                  The sunroof drain is on the right , if we had bladerunner technology we could rotate the point of view inside the arch
                  The red arrow is pointing to the location of the rear sunroof drain hose.

                  Thanks Eric.
                  RS2'd 93 UrS4 5 spd sedan
                  94 UrS4 V8 6 spd manual avant

                  Comment


                  • #10
                    Throwing you a bone Dave......

                    My RS2 doesn't have a sunroof, but the RS2 that donated its rear bumper did.

                    Pics are from HERE









                    Comment


                    • #11
                      Drain plug 4D0 877 242 B is the one. I could not find a special one like I have with the registration plate light wiring passing through it anywhere and I don't remember seeing a part number on mine. I'm in California ATM or I would check.

                      Comment


                      • #12
                        1995 Avant Rear Drain for Sunroof






                        I cannot explain the logic of putting it there
                        Attached Files
                        Eric

                        95 S2 Avant under rebuild.

                        Comment


                        • #13
                          Originally posted by saltinot View Post
                          Drain plug 4D0 877 242 B is the one.
                          Thanks Tom. That PN is very common across the B3, B4, B5, C4, etc. models. Appears to be the same one used at the base of the "A" pillar to drain the front sunroof cassette corners.

                          Attached Files
                          RS2'd 93 UrS4 5 spd sedan
                          94 UrS4 V8 6 spd manual avant

                          Comment


                          • #14
                            Originally posted by irishs2 View Post
                            1995 Avant Rear Drain for Sunroof.
                            I cannot explain the logic of putting it there
                            Based on Tom's post, I don't know if it was supposed to be there. Certainly appears like if it was there on earlier models, they changed it to behind the bumper like the C4 avants.
                            RS2'd 93 UrS4 5 spd sedan
                            94 UrS4 V8 6 spd manual avant

                            Comment


                            • #15
                              Eric, that makes a heck of a lot more sense than running it down the D-pillars. I honestly haven't notice those outlets in the fender well. I know what I am checking out once I get home. Thanks for sharing!

                              I believe Eric is correct. They must have just used the grommet/drain plug to get the job done with the registration plate wiring on the RS2.

                              Comment

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