Humming Noise when I let off the gas

ChaseMan777ChaseMan777 Member Posts: 3
edited October 2018 in Cadillac
I get a humming noise when I let off the gas between 25 and 45 MPH. There is no vibration. The breaks are new; wheel bearings new; transmission new. Perhaps some kind of vacuum leak??? Anyone have a clue on this one?


  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    edited October 2018
    Is the noise from the front of the car or the rear? High up or low down? Does the noise decrease as the car slows down? How many miles on this car?
  • ChaseMan777ChaseMan777 Member Posts: 3
    It's coming from the front of the car. Sounds like a low flute note. We just had the car smogged and some part was replaced between the engine and the firewall.
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Oh, I'm wondering if this is some part of the EVAP emissions control. If they are leaking or have a faulty valve, they can make that type of noise. You might want to locate the EVAP canister and see if it's up front, about where the noise is.
  • ChaseMan777ChaseMan777 Member Posts: 3
    Mr_Shiftright, I think you're pointing me in the right direction. The part we had replaced was the "Air Intake Coupling" which was causing an orange light on the dash, and the car wouldn't pass the smog test. So we had this part replaced (which wasn't very expensive) but the labor was $800.00. That solved the problem, and we passed the smog check, but only a week later we have this strange humming sound when I let off the gas. It happens at 17 mph and higher. Let off the gas and you get this flute like sound that's very annoying. Do you think an "Air Intake Valve" could cause these symptom?
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Not sure what that is--is that what is called the "purge valve" for the EVAP system? If you think about it, isn't a flute basically a valve opening and closing with air passing through it? That's exactly what an EVAP system does.

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