Blocked drain holes on a6 c5 2.4 auto avant flooded interior

[JAAUDIA6]

I have a 2004 A6 2.4 Avant which seemed to have blocked drain holes in the engine bay.
I park my car on my drive which as a 30 degree slope facing upward. This morning I found that the rear footwell passenger side had 4" of water in it, on top of the factory fitted mats as well. When I checked the engine bay, the battery compartment was also full of water, I believed that the drain plug is located below the battery, so took the battery out and poked around a bit then whoosh! what seemed like gallons of water disapeared under the car.
My question is:- Is that the only drain hole or are there any by the wings or another one in the engine bay? Will what I have done stop water getting into the cabin? or are there any other drain holes I should be looking for?

[Sam]

There are two drain holes in the plenum chamber, one near the battery and another towards the centre of the car near the brake booster.

[NickPicks]

You also need to lift the front passenger carpet, dry it out and check the central convenience module for water damage.

This is a common A6 C5 problem, which can be expensive to fix if not caught early enough.

[nigelbb]

I had the same problem with my Quattro 2.7T about three months ago but to my regret did not lift the carpets & get all the under felt dried out properly which resulted in a bill of £770 for replacing the Tiptronic gearbox ECU last week. I just mopped up with old newspapers & cloths but clearly while it was dry on top it was still damp underneath. I managed to push the rubber drain plugs out while I was clearing the leaves so hopefully I will not encounter the problem again.

[NickPicks]

The only problem with removing the plugs completely is that you might suck engine fumes into the plenum chamber and into the car through the air conditioning. Whetehr you think this is better or worse than the risk of water ingress is up to you.

[Golf tdi Hal]

Has anybody had any luck poking/clearing the rubber bungs in the drain holes without removing the battery? I am feeling lazy and the weather is crap...

[NickPicks]

It only takes about 30 minutes to do the whole job including removing the battery. Even if you don't have the radio code, you can use a lighter socket battery saver.

I expect you could poke something thin and wiry down the hole, but I don't know whether it'd do as good a job as a crafty finger.

[Sam]

You can do it from beneath the car too but wear a diving mask, snorkel and something with elasticated cuffs.

[big1pie2003]

Just cleaned mine out, one of them things that I started doing when I service the car. Glad I did as the thing was jammed full of leaves etc.

Took me about 30 minutes and I cleaned everything with rag. I only cleaned out the one under the battery tray as I didn't realise there was a second drain hole.

Whereabouts is the convenience module? Is it that box full of electrickery next to the master cylinder and servo?

Pat.

[NickPicks]

No, the CCM is under the carpet just in front of the front passenger seat.

The second drain hole is under the brake servo. You can reach it quite easily.