Strange Noise

[sotondjt]

I've been plagued by a strange whine from the car. Mostly when it's cold at low speed. It sounds like a pump or motor running. Sometimes it runs for a second and other times it runs for a minute. It only happens when its cold.

I found a US forum post that has the same symptom. Has anyone in the UK had it?
https://www.audiworld.com/forums/a4-b9-platform-discussion-212/weird-noise-2914541/


It's quite random and it didn't do it when the dealer had it in last week.

 

[Jcbmally]

Is it making the noise when you are braking ??

 

[Retroman]

Possibly a small auxiliary water pump circulating warm coolant around the cabin heater system? At increased engine speed the main mechanical water pump would push water around more vigorously but no so well at lower engine speeds and the cabin heater system is likely to be triggered by some sort of temperature control - hence the occurrence when cold.

Auxiliary water pumps are used for a variety of reasons:- 1) Commonly to efficiently pump coolant around a cabin heater system e.g. some BMWs 2) On some high performance Audi engines to cool the turbo for a few minutes after turning off the engine and 3) On certain common rail diesels like mine to pump coolant around the EGR system.

 

[sotondjt]

It happens both on braking and accelerating. Interesting idea about the auxiliary pump. It's a petrol so not sure if they have aux heaters?

 

[cuke2u]

Petrol cars do have electric coolant pumps to cope with start/stop conditions. Diesels only have auxilary heaters, usually called supplementary or ptc heaters...