SCUBES

Is it the fuel pump priming?

growl2

I do not know exactly the noise you are hearing. I do know on my A6, occasionally after I shut the engine down and got out of the car, I would hear a series of clicks with an electric motor sound come from the back of the car. I subsequently learned it is normal and has something to do with the parking brake. I did hear the same noise come from my 2011 S4 once (only has about 1500 miles). I do not know if this is the noise you are hearing but I know it confused me for quite a while and certainly sounded similar to a fuel pump priming.

Excelsior7

My 335 would make a similar noise after I opened the door. I always assumed it was the fuel pump, or some other part of its "wake-up" procedure.

After the car was shut off, there was a whining noise from the oil being circulated through the engine (Turbo cars with oil-cooled turbos require this. Turbo timers are the aftermarket solution)

Is the S/C oil cooled? the S4 may have a similar mechanism, though I'm betting it's a fuel pump. That makes the most sense.

clord

Mine has done that as well, from new. Seems to do it when doors are opened, too. The sound definitely seems to be coming from the rear area, but, I doubt it's the fuel pump.

redrocker55

I asked one of my senior service technicians about this and they told me it was def the fuel pump priming the injectors. My guess is it's part of the direct injection system and the higher fuel pressures required for these injectors/combustion process...speeds starting the engine...less work for the starter/battery.

ItsDubC

This happens on my B8 A4 as well.

I'm not convinced that it's the fuel pump priming tho, since I mostly notice it after I've just turned the car off, opened the trunk to take stuff out, and closed the trunk lid. Plus, it seems to be coming from the rear.

I hear a different sound (more like a robotic movement than a tick-tock-tick) coming from the front when I open my driver-side door to get in to start the car, and I was always under the impression that this is the sound of the fuel pump priming.

growl2

I get both noises. As I note above, pretty sure the one from the back is related to the electronic parking brake. One in front is the fuel prime. Question that starts the thread is regarding the one in the rear as you note.

Zed 2.0

Neither the parking brake nor the fuel pump makes a ticking/clocking noise. Fuel pump priming sounds almost like a camera flash recharging -- high pitched and kind of electronic. The parking brake is lower pitched and sounds more like a drill. Neither should happen when you close a door, either (fuel pump sometimes primes when you open a door).

GiantEli

I was under the impression that it was the opening/closing of external air "ports" (or whatever they're called...I'm not a plumber), essentially helping to seal the interior off from outside air once locked.

growl2

I agree that the parking brake noise is not triggered by closing the door. Was thinking more coincidental timing when getting out of the car. As for how to describe the different noises, I will defer to others and am just glad I am not a service writer or mechanic trying to understand different descriptions.