GRAYZ

I use to own a 98 SS M6 and now own an 02 Z28 A4.
I use to only drive my Z once a week but now that my daughter turned 16, she is driving my daily driver and I drive the Z every day.

Anyway, when I am in OD or D at a light idling with the windows rolled up, you can hear a loud hum. It is a tad bit louder when the air conditioner is on. When I put it in neutral, the sound immediately stops. I guess I have just noticed the hum because I am driving it everyday now.

I assume this just from the drivetrain on the A4? I dont remember noticing this humming noise on my M6. Any comments, the Z has 33,500 mile on it.

Aic

I have a similar hum at idle sometimes. Have you figured outn what it could be yet?

GRAYZ

I just changed out my stock muffler with a Magnaflow and replaced the exhaust pipes with 2.5" pipes and added new Fast Toys Stainless Steel Z28 tips. I dont think I hear the hum anymore. It was somewhat intermittent but it very well may have been when the AC and fan was running at the same time and the stock muffler was doing some kind of humming/resonating. It sounded like a vibration kind of hum but I did not feel any vibration.

I cant say I have heard the hum after I changed out the exhaust, maybe because I have been so attune to listening to the sweet exhaust note I will have to listen out for it and see if I hear it again. I will keep you posted...

jdustu

iTrader: (2)

my car makes so many noises that i don't even pay attention anymore......maybe it's the fuel pump? that's kinda high pitched, though.....

transamws686

iTrader: (4)

is it almost like a whistle, it may be since it is so hot that the fans are running hard, this is especially so if the ac is on.

GRAYZ

Since I replaced the exhaust, I kind of hear a faint hum every now and then when the fan and AC is on but not like it was with the stock exhaust. I think it was the stock muffler resonating because it sounded like it was coming from the rear.

GRAYZ

Just like I replied above, I think it was the stock muffler resonating when the fan and AC was on. It was very intermittent. Now I sometimes hear it at idle but it is very faint that I dont even notice it. Like you said the combo of the fan running hard, AC humming, and stock muffler resonating. Mine was not a whistle, definately like somebody humming in your ear. Kind of filled the whole cabin. That is why I think it was the stock muffler resonating.

t1blackout

iTrader: (6)

I hear the same noise in my car, I know what you mean. Does it go off when you slightly press on the gas? I have no idea what it is.

GRAYZ

Yes, mine only happened when the car was in gear at a stop light and it was intermittent. I could put it in neutral and the hum went away.

SmokingWS6

iTrader: (1)

hmm. If the high fans are on in an A4 sometimes the voltage will drop a bit at idle in drive, perhaps your hearing the fuel pump or fans whining, the pitch will change as the voltage drops a bit. Thats about the only thing I can think of.