Plastic water pump and thermostat housing failure
Attaches to CDNC at engine level · Cooling · carried by 2 variants across 2 chassis
Overview
Plastic water pump and thermostat housing failure is a common fault recorded against CDNC at engine level, typically from 90–160k km. It shows up as coolant loss with no obvious puddle, temperature warnings, coolant smell after a run. Where it's documented, the repair runs €400–€800 (independent, pump and thermostat as one job, costs dated 2026-07), and it can be checked before you buy. 2 variants across 2 chassis in this database inherit it.
What happens
Symptom. Coolant loss with no obvious puddle, temperature warnings, coolant smell after a run.
Cause. The composite pump and thermostat housing crack and the pump seal fails. It's a routine wear item on this family rather than a defect.
Sources. specialist reports
How to check it
Static checks
Look for dried coolant crust around the pump and the front of the block, and check the expansion bottle level against the marks.
Engine off, ideally on a lift.
Every variant that carries this
| Variant | Chassis | Body | Years | Risk | Good buy | Cost as % of good buy |
|---|---|---|---|---|---|---|
| 2.0 TFSI CDNC | B8 | sedan | 2008–2012 | R5 | €4,300 | 14% |
| 2.0 TFSI CDNC | B8 Avant | wagon | 2008–2012 | R5 | €4,500 | 13% |
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.