M.l. Ali

I own an Audi A6 2015 model 2.0T, S-line, which I purchased as a brand new car 3-4 months back. The car has 5,500 kilometres on its mileage.

The car is presently in the workshop for diagnosis and resolution of the following problem. .

There is a damp/low knocking noise coming from the front suspension or engine sounding like a loose component in the suspension or engine hitting against the car chassis. However there is no vibration either in the steering or the wheels.This sound happens ;

• When the car is cold. Once I've driven the car for 2-3 kilometres it disappears.
• When the car is being driven on a pavement or rough surface.
• When the car speed is below 20 KMs.

This sound only became audible during winters and that too in the morning only. Due to such a temporary nature of the sound Audi engineers are having trouble with diagnosis.

If someone here has had a similar experience and ended with some sort of a solution I would really appreciate if you share the knowledge.

jasonlitka

How cold is it? Might be ice that formed over night and then melts as the car heats up.

Kris Hansen

This sound happens even if you are not driving over bumps? MY best guess is there is something that is just a bit loose when very cold, and as it warms up even a little, due to expansion, becomes tight again.

M.l. Ali

Hey thanks for the reply guys.

@ Jason: By cold I mean below 15 Degree Celsius. I wish there was ice forming up but unfortunately I live in a warm region.

@ Kris: The sound is audible only when driving below 20 km/hr.

jasonlitka

I'm going with Kris on this one then.

After leaving your car overnight, start it up in the morning and let it idle until the engine is fully warmed up. Take the car out and see what happens. If the noise is gone then it's the engine or something very near. If not, then it's likely part of the suspension.

Kris Hansen

It could also be tire related - summer tires will become quite stiff even at above freezing, sitting overnight they could take a "set" and have temporary flatspots that work out as you go down the road. They might not be enough to feel, but might be enough to hear.

M.l. Ali

I left the car for 5 days at the Audi Workshop. They have checking the suspension, the exhaust and probably engine mounts as well. Couldn't trace the problem.

@ Kris: someone actually mentioned the same thing happening with the tyres like you did. I will pump up the tyre pressure for one day to see if it resolves the problem.

DB22

Post your location, preferably in your signature, so that others in similar areas of climates may post their experiences.

13c7a6

Did they check for a loose heat shield?

jasonlitka

Good one. That's likely to be a higher-pitched noise though, more like a ticking or a chatter. My Infiniti used to do that during the cold until they replaced the missing bolt.