Car Model Guide/ Issues/ Plenum drain blockage and module water damage

Plenum drain blockage and module water damage

Attaches to B6 at chassis level · Electrical · carried by 10 variants across 2 chassis

Overview

Plenum drain blockage and module water damage is a common fault recorded against B6 at chassis level, typically from 80–200k km. It shows up as damp or soaked carpets, misted windows, and electrical faults that come and go as water reaches the control modules under the seats and in the footwells. Where it's documented, the repair runs €0–€1,200 (free to clear the drains, module replacement and coding if water has reached them, costs dated 2026-07), and it can be checked before you buy. 10 variants across 2 chassis in this database inherit it.

€0 – €1,200

free to clear the drains, module replacement and coding if water has reached them · costs dated 2026-07

Likelihoodcommon

Typical onset80–200k km

Detectableyes

Walk awayno

Evidencedocumented

What happens

Symptom. Damp or soaked carpets, misted windows, and electrical faults that come and go as water reaches the control modules under the seats and in the footwells.

Cause. The drains in the plenum chamber under the windscreen block with leaves and debris, and water then overflows into the cabin. The comfort control module sits low enough to be soaked, which is where a cheap fault turns expensive.

How to check it

Static checks

Lift the carpets front and rear and press for damp, check under the seats for corroded module connectors, and clear the plenum drains yourself before you buy.

Engine off, ideally on a lift.

ElectricalcommonDetectable at viewingevidence: documented80–200k km

Every variant that carries this

Variant	Chassis	Body	Years	Risk	Good buy	Cost as % of good buy
1.9 TDI BKC	B6	sedan	2005–2008	R2	€1,750	34%
1.9 TDI BKC	B6 Variant	wagon	2005–2008	R2	€1,850	32%
2.0 TDI BKD	B6	sedan	2005–2008	R3	€2,100	29%
2.0 TDI BKD	B6 Variant	wagon	2005–2008	R3	€2,250	27%
2.0 TDI CBAB	B6	sedan	2008–2010	R4	€2,500	24%
2.0 TDI CBAB	B6 Variant	wagon	2008–2010	R4	€2,650	23%
1.4 TSI CAXA	B6	sedan	2007–2010	R3	€2,000	30%
1.4 TSI CAXA	B6 Variant	wagon	2007–2010	R3	€2,150	28%
1.8 TFSI CDAA	B6	sedan	2007–2010	R3	€2,400	25%
1.8 TFSI CDAA	B6 Variant	wagon	2007–2010	R3	€2,550	24%

The last column is the point. The same repair is an inconvenience on one variant and a reason to scrap the car on another. A failure costing a quarter of the vehicle's value changes the purchase decision regardless of how rare it is.