Strange Ticking Noise in Engine Bay

B8 S4
#1

Installed the AMS CPS system and while I was attempting to bleed air from the coolant system, this periodic ticking noise started at idle. It would go away whenever I revved the engine. I heard it from inside the cabin with the hood popped. I was initially scared that it might be pinging (even more so after a conversation with a friend here), but then spoke to another friend who works at Bosch and he thinks it too periodic to be pinging, it’s also happening at idle rather than with load.

FWIW I haven’t driven the car much in the past month and the gas has probably been in there for that entire period. Any guesses as to what’s going on? Just DI pump noise, which is strange since it goes away? My guess is something to do with the SC loop pump?

https://www.youtube.com/watch?v=l5MALuDQSqQ

Thanks guys. I can make a better video to show the transition between the noise going on and off.

#2

Vid is private

#3

Fixed, sorry bout that…

FWIW I have a stg 2 APR tune, so not stock software + calibration.

#4

It does seem a tad louder than normal

#5

I’ll try to make a video of it transitioning between quiet/loud.

#6

almost sounds like an injector ticking (would explain why it goes away when you rev engine) - but doesn’t correlate with installing the cooling sys.

#7

Sounds like the standard injector ticking albeit a bit louder

#8

The thing that had me confused was how it got noticeably louder and went away via pedal input, otherwise, I would have just assumed normal DI tick.

But thanks all for chiming in, much appreciated.

OK, just drove around town and heard nothing inside the cabin, I’ll assume this is just something with the DI pump, maybe it has separate modes? I’ll try to keep my ears open but I think it’s much ado about nothing…

#9

These videos show it well:

https://www.youtube.com/watch?v=qxDex8FVrkY

from inside (turns on around 15 sec and then again at 30 sec)

https://www.youtube.com/watch?v=dhJ41heXYEk

I’ve never heard anything like that while driving the car…the onset seems too abrupt to be knocking, it’s got to be some kind of pump?

#10

Sort of subject,
How do you like the alpha CPS? Install go fairly easy and did you get instructions with the system…?

#11

Haha fair enough, first off that was a killer price alpha sold them for, so kudos to them…install went pretty easy, except for the riv-nut installation. But it seemed like they actually set when I mounted the reservoir.

The real adventure for me was feeling like I properly bled the system of air. The alpha instructions were pretty bad in this regard. I stripped the supercharger air bleed screws, which are made of some kind of soft plastic/neoprene stuff. Then I realized that you can’t have any of the bleed screws open while the alpha pump runs (goes on with accessory power).

My hope now is the system will burp itself and I’ll add minor amounts of coolant as needed. No real idea about how the system performs, since I’ve been scared to run the car hard due to this weird noise and wanting to make sure most of the air is out of the system lol. Have a track day at the end of the month, so now I’ll try to put on some miles. Might try to meet up with Jeff and/or Muneeb to go to milan to see any difference on the 1/4 times.

I’ll make a thread here or on AZ about my impressions, since I think alpha deserves the feedback.

#12

Thanks, good luck with the ticking. I def heard it on the video but have no clue, although like some of the others before said it does sound like some “amplified injector pulse”. Keep us updated with your findings. I would definitely take it easy until it’s sorted out. I’ll keep in eye out on your review very interested on this system. Missed the group buy deadline by a few days smh. Isn’t paying attention.

#13

Just heard back from the dealership, this was their explanation, which seems to make sense

“I just listened to that with my shop foreman and we both agreed that then noise you are hearing is coming from the purge valve. It is purging excess fuel vapors from the system when you hear that kick in. It generally is only kicks in @ idle and will be much more noticeable with the hood open. It is normal operation of that system as long as the check engine light is not on. Please let me know if you have any other questions.”

#14

whoa. didnt know such a thing existed. how does that work?
And where does it purge to?

#15

All I really see about it is here: http://www.samarins.com/glossary/purge-valve.html

It’s interesting that the sound would be periodic like that, maybe a PWM signal of sorts that partially opens the valve. Don’t really know.

The reason why this explanation seems OK is it aligns with the change in throttle position, even if it’s only at idle.

#16

Forecast for April 22nd looks promising and they have a TnT. I should be able to get there around 6:30pm. I’ll text you around then to see if you’re free. I’ll PM Jones as well to see if he can make it out

#17

I might try to go to Milan tomorrow. I’m getting the car setup this weekend for a track day on April 25 and not sure I’d want to run it on the drag strip a few days before. But we’ll see.