Avant rear sunroof drain?

[Nobby]

Evening all.

Have a tiny damp patch rear pillar by the boot so I thought I’d investigate today whilst it’s sunny.

Doesn’t seem to be coming out from the aerial on the roof so thought I would check the sunroof drains.

Front ones are easy to find and run clear. Rear ones though…. Where the chuff are they? According to the Bentley manual they come out by the rear bumper (directly under the wet patch) but it only shows a saloon version.

Tried pouring some water in both sides and it just leaked out by the pillars in both sides. I can’t remember seeing any pipes when I took the bumper off last time. Unless it’s behind rhe rear arch liners?

Any ideas before I start pulling off the pillar covers?

[Shoppinit]

I thought there were only the 2 drains, left and right that come out in front of the doors.

Where’s your damp patch? Oo er.

[Nobby]

Wet patch is on the pillar by the boot lid. D pillar?

This is what the Bentley manual shows.

Here’s a quick photo of the sunroof from an A6 C5. Min should be the same but is a solar one (ooo errr get me )

I’ve circled both the drains. Back one probably isn’t visible when looking into the sunroof. It’s got a white section with a small white tube in each corner.

[Shoppinit]

Huh. Well you live and learn.

I would have thought that if your car parked reasonably horizontally, as I suspect yours is, then the front drains would do the job.

/This is why I hate sunroofs.

[Nobby]

Ah. But it’s not parked level. Slight incline to the rear (and I don’t like reversing into the drive as when I do the startup makes the garage door rattle)

I might have a look underneath tomorrow. Found a video of an an A4 and the owner says the hoses pop over very easily.

D’oh!

[Nobby]

Right all sorted (I think).

Sunroof does indeed have 2 rear drain pipes but contrary to the Bentley manual then don’t exit down by rhe rear bumper and don’t go down the D pillar.

They actually go down inside the C pillar. You’ll only be able to see the very top as the rest is pretty much hidden. They also exit at the top of the rear wheel arches.

Here’s what I found on mine.

If you have any damp patches at the rear pillars then it’s most likely the rear drains are blocked. Water fills up the pipes and overflows out the channel onto the inside of the headliner. The headliner is pretty substantial and although not waterproof the water seems to flow to the lowest point. As my car is always parked front higher it flows backwards.

At first glance thought I might need to completely remove the headliner. Glad I didn’t though. The rear drains are pretty far back and you can’t see them through the gap when the sunroof is open

Thinking that my drains might have popped off I decided to lower the rear half of the headliner to get a cleared view.

To do this you need to remove 5 bits of interior trim. Both D pillars first. Then the rearmost trim above the boot. Then the two bits of trim over the back doors. These are all kept in with a combination of screws and clips - some pretty well hidden. They are plastic though so don’t bend them too much.

With all the removed you can pull out the boot light too and pull the headliner down slightly. This is what you’ll see.

View from boot

The circled bits are the two rear drains.

Rear drain location

As you can see the pipes disappear behind the airbags and down the C pillar. I decided to disconnect them here and run a pipe cleaner down them. After doing that water came gushing out the wheel well (from all over the place) so I must have got rid of the blockage. I tried it a few times and also ran some compressed air down. I still couldn’t locate exactly where the exit was though and the pipe cleaner had an abrupt stop about two foot down the pipe. One the joins at the drain had a teenie tiny drip so I sealed both of them with some heat shrink too.

Drain with better seal

Now to find the exit. With the wheel removed I then got rid of the wheel arch liner. Still not 100% obvious (like the front ones which exit in a nice green pipe down the a pillar). Removed this bracket and the grommet is behind it. Think this is the TPMS receiver so there’s one on each side.

TPMS receiver and grommet behind

With this removed this is what you see.

Rear drain exit

So there you have it. Seems to drain really nice now. Ready for a storm tonight so will check tomorrow if it can cope with the rain.

Here’s some more photos with the trim removed incase anyone has issues with airbags etc. I also found a random wire going round my boot trim. Traced back and it goes to the loom?? One wheel arch also had a false widow spider in it

I should also add that I have a solar sunroof but the normal
Sunroof isn’t much different.

If you want to clean the rear drains I’d suggest removing the rear wheel arch liners and cleaning the gromit first. Mine didn’t have any gunk at the sunroof bit but looks like the gromit is easily squashed and blocked.

[Shoppinit]

What an incredible faff!

[steve2003rs6]

Always wished I had the sunroof option. Now I am pleased I don’t have one.
Really nice work Nobby and a great write up.