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D2 - Common Faults Quick links to all known common faults and their solutions

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  #1  
Old 9th October 2015, 09:38 AM
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Default Possible Reason for Passenger Side Water Ingress

I have had 3 A8's now over the last decade, and for reasons I could never get to the bottom of, all of them had water coming in to the passenger side.

I suffered this with the last two, however on my current one, I decided to get quite invasive with it and try to find out what the problem was.
I asked my garage to investigate this, and the obvious culprit was the drain holes and tubes being blocked.
They checked everything - including the sunroof drain - nothing. All of the drain tubes were clean and clear.
Sadly at that point we couldnt come up with anything else.
Last year, the Indicator relay blew, so I had to have it replaced, and during this investigation they found the reason it blew out was, it was full of water. The leak seemed to be coming in around the passenger side windscreen area and was dripping on to the electrics.
We replaced the Relay and sealed it before refitting so it didnt fill with water again however it didnt explain why or what was causing the leak.

I went to get my daughter from school earlier this year and while waiting, a guy was finishing work and got chatting with me as he was a A8 enthusiast.
About half way through the conversation he asked what kind of issues I had with it, and I mentioned the soggy passenger side.
He simply said "I know what the issue is there. Its the windscreen"

He explained he had a friend who worked in the trade who adored his A8's and the first thing he did when he got one in was have the windscreen replaced.
Doesnt explain why its always the passenger side though, but and I dont know how true this is, but it seems very logical...
At the factory, they use Robots to put the mastic on the windscreen, and then the same robot fits it.
When applying the mastic, it starts in the bottom left corner, goes around the outside of the window to end up in the bottom left corner.
That bottom left corner is where there is a slight joint, which is actually sealed when the windscreen goes in, but because its so accurate, there is a weak spot there.
Over a period of years, the mastic dries out and shrinks. Where you have a constant line, it remains sealed but where the joint is, it cracks and starts to let water in.
Hence why all the A8's I have had, have that issue on the passenger side.

Now, I will admit, its a very aggressive way to fix the problem in having the windscreen replaced and there are known issues with the drain points blocking up and that is certainly worth checking first, but if you get to the point where you have confirmed all the drain holes are clean and the problems still there, its is most likely the windscreen thats letting the water in.
If you do get it replaced you need to urge the glass fitters to go to town though, as I have previously had a windscreen replaced and they didnt seal it correctly and water came in even worse.

I hope this helps
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Old 9th October 2015, 02:18 PM
mannyo mannyo is offline
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I would suggest you do a google search for "Botangs Hole", essentially its located underneath the ECU box and is made of paper. it eventually fails leading to water getting into the car on the passenger side.

http://forum.a8parts.co.uk/showthread.php?t=3281
http://forum.a8parts.co.uk/showthread.php?t=7645
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Old 9th October 2015, 05:00 PM
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>>Last year, the Indicator relay blew, so I had to have it replaced,
>>and during this investigation they found the reason it blew out was, it was full of water.

100% this is Botang's hole. Second link above, 1st picture.
Also check your ABS relay, which is near the indicator relay. Probably full of water as well.
This is not a windscreen issue.
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Old 12th October 2015, 07:48 AM
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+1 for Botangs Hole

However the picture that Notorious refers to is from a left hooker and is difficult to work out where it actually is. On the RHD are 2 HVAC pipes that run up the passenger side that hinder your view and access . I found it easier after i removed the bonnet strut.

Photos from RHD in the same post but page 2
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Old 16th October 2015, 02:59 PM
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Okay - eats my slice of pie and another story.

I did search the forum for any possible information on water ingress before I posted this up, and sadly found nothing (which considering everything that was here is a bit of a surprise...).
After reading about this Botangs hole I popped out, and had a look... couldnt see anything but regardless, phoned my garage and booked it in for today.
Went down this morning armed with the forum thread, and the rough location, we got the lights out, disassembled a few things and made a start.
For 10 minutes, it was lots of "cant find it" until suddenly he goes "oh... its there". It was actually about 3 inches from where we were looking, and to my horror there wasnt anything on it at all - it was wide open and almost like it was in the forum pictures.
From there, a small galvanised metal plate was fabricated, loads of sikoflex type material applied to it, and then with the help of a magnetic probe and few screw drivers it was positioned and then pressed down and sealed.

I have to say, I was shocked.
Audi produce superbly engineered cars design wise, and for them to be so half arsed about this item is out of order. This hole as rightly stated, is right above a major part of the cars electrics, and almost directly below the windscreen scuttle drain off. Its almost as if they placed it on purpose to pour water in to the passenger side and when I looked at mine, there was nothing covering it at all - the paper that had covered it had long gone.

I am pleased I posted this here though as even if I was wrong, this is a common problem on A8's and now perhaps this will help a few people realise there this problem is there and how to cure it.
Overall, it took about 30 minutes of faffing around in the garage and I although it has yet to throw it down, I hope this has cured my soggy passengers.

Now all I have to fix is the passenger wing mirror (peeled antiglare film), the CD changer (not working - coming up with Error on the dash and its not even bothering to load the disks), the rear tow eye cover (snapped retainer) and my Quattrosport will be after a wash and a valet, mint again.

Thank you for pointing out this Botangs hole though... very helpful.
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Old 16th October 2015, 03:29 PM
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That's a great bit of feedback. It's always good to hear back, success or failure. Its this that rewards the contributors for their efforts and improves things here
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Old 16th October 2015, 04:57 PM
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Check relays neighbouring to indicators relay.
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Old 16th October 2015, 05:49 PM
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We pulled them out to check - no water in them and there are no electrical issues so hopefully when this is dried out I will be much happier.

One top tip I have though for moisture in the cabin are some handy little ... err... water trapping bags... I cant come up with a better name.

They are sold in asda as demisting aid. They are fabric bags full of water absorbing material. You put them out in the car, and it helps stops your windows fogging in the mornings.
Nice thing is, they are rechargable. They have a colour code on them. When its Blue its ready, when its pink, its full of water.
You simply take it in the house, put it in the microwave for 6 minutes - this heats it and removes the water... after that you put it back in.
I have just recharged the two I had and put them back in to help get rid of the moisture in the car.
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Old 22nd October 2015, 10:19 PM
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Well, I thought I best give a quick update on this - I am pleased to say after the heavy rain of the last few days, I checked under the carpets today and there is no water and its dry as a bone, so it looks like this was a very accurate diagnosis.

Big thank you for pointing this out
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Old 23rd October 2015, 07:25 AM
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